Search

UnlabelledThis position paper reviews how the National Bone Health Alliance (NBHA) will execute a project to help assure health professionals of the clinical utility of bone turnover markers; the current clinical approaches concerning osteoporosis and the status and use of bone turnover markers in the USA; the rationale for focusing this effort around two specific bone turnover markers; the need to standardize bone marker sample collection procedures, reference ranges, and bone turnover marker assays in clinical laboratories; and the importance of harmonization for future research of bone turnover markers.IntroductionOsteoporosis is a major global health problem, with the prevalence and incidence of osteoporosis for at-risk populations estimated to be 44 million Americans. The potential of bone markers as an additional tool for health care professionals to improve patient outcomes and impact morbidity and mortality is crucial in providing better health care and addressing rising health care costs. This need to advance the field of bone turnover markers has been recognized by a number of organizations, including the International Osteoporosis Foundation (IOF), National Osteoporosis Foundation, International Federation of Clinical Chemistry, and Laboratory Medicine (IFCC), and the NBHA.MethodsThis position paper elucidates how this project will standardize bone turnover marker sample collection procedures in the USA, establish a USA reference range for one bone formation (serum procollagen type I N propeptide, s-PINP) and one bone resorption (serum C-terminal telopeptide of type I collagen, s-CTX) marker, and standardize bone turnover marker assays used in clinical laboratories. This effort will allow clinicians from the USA to have confidence in their use of bone turnover markers to help monitor osteoporosis treatment and assess future fracture risk. This project builds on the recommendations of the IOF/IFCC Bone Marker Standards Working Group by developing USA reference standards for s-PINP and s-CTX, the markers identified as most promising for use as reference markers.ResultsThe goals of this project will be realized through the NBHA and will include its governmental, academic, for-profit, and non-profit sector stakeholders as well as major academic and commercial laboratories. Upon completion, a parallel effort will be pursued to make bone turnover marker measurements reliable and accepted by all health care professionals for facilitating treatment decisions and ultimately be reimbursed by all health insurance payers.ConclusionsSuccessful completion of this project will help assure health professionals from the USA of the clinical utility of bone turnover markers and ties in with the parallel effort of the IOF/IFCC to develop worldwide bone turnover reference ranges.

Bone markers are useful tools for managing bone diseases because they provide information that differs from but complements bone mineral density measurement. Problems in the measurement and interpretation of bone marker values continue to hamper the optimal utility of this clinical tool.Most of these difficulties originate from problems related to the handling and control of analytical and biological variability of bone marker measurements. These sources of variability can be substantial and need to be controlled.Certain bone markers or bone marker tests may require special considerations, such as analyte stability. Guidelines for minimizing preanalytical variability have been developed, and the means to minimize the analytical variability for some bone markers are available. [ABSTRACT FROM AUTHOR]

Aim: Lipoprotein (a) [Lp(a)] is a well-established risk factor for cardiovascular disease independent of low-density lipoprotein-cholesterol (LDL-C). The Lp(a) concentrations were inconsistent between the immunoassays. This study aimed to investigate whether harmonization of Lp(a) measurements can be achieved using a serum panel value assigned with the IFCC-endorsed mass spectrometry-based reference measurement procedure (IFCC-MS-RMP)., Methods: We measured the Lp(a) concentrations using five Lp(a) immunoassays in 40 panel sera provided by the Centers for Disease Control and Prevention (CDC), and 500 Japanese subjects enrolled in the Bunkyo Health Study. Of the five immunoassays, only the Roche Lp(a) assay was traceable to the WHO-IFCC reference material SRM2B. Lp(a) concentrations in CDC samples were also determined by IFCC-MS-RMP, provisionally calibrated to SRM2B. Lp(a) concentrations were expressed in mass units (mg/dL) for most reagents, but in SI units (nmol/L) for Roche's reagent and IFCC-MS-RMP., Results: In the CDC panel sera, all immunoassays, including Roche's reagent, showed good correlations with IFCC-MS-RMP. In the Bunkyo Health Study samples, all immunoassays showed good correlations with Roche's reagent (r s , 0.986-0.998) although the slopes of the regression lines ranged from 0.292 to 0.579. After recalibration with the CDC's panel sera, Lp(a) results of Bunkyo Health Study samples were converted to the equivalent values determined by the IFCC-MS-RMP, thus resulting in a marked reduction in the intermethod CV among the assays., Conclusion: We achieved harmonization of Lp(a) measurements with five immunoassays using a serum panel value assigned with the IFCC-MS-RMP.

Background: In previous publications, the Task Force on Reference Measurement System Implementation proposed a procedural approach combining a critical review of entries available in the Joint Committee on Traceability in Laboratory Medicine (JCTLM) database with a comparison of this information against analytical performance specifications for measurement uncertainty (MU) and applied it to a group of 13 measurands., Content: Here we applied this approach to 17 additional measurands, of which measurements are frequently requested. The aims of the study were (a) to describe the main characteristics for implementing traceability and the potential to fulfill the maximum allowable MU (MAU) at the clinical sample level of certified reference materials and reference measurement procedures listed in the JCTLM database; (b) to discuss limitations and obstacles, if any, to the achievement of the required quality of laboratory measurements; and (c) to provide a gap analysis by highlighting what is still missing in the database. Results were integrated with those obtained in the previous study, therefore offering an overview of where we are and what is still missing in the practical application of the metrological traceability concept to 30 common biochemical tests employed in laboratory medicine., Summary: Our analysis shows that for 28 out of 30 measurands, conditions exist to correctly implement metrological traceability to the International System of units and fulfill at least the MAU of the minimum quality level derived according to internationally recommended models. For 2 measurands (serum albumin and chloride), further improvements in MU of higher-order references would be necessary., (© Association for Diagnostics & Laboratory Medicine 2024. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Introduction: An error grid compares measured versus reference glucose concentrations to assign clinical risk values to observed errors. Widely used error grids for blood glucose monitors (BGMs) have limited value because they do not also reflect clinical accuracy of continuous glucose monitors (CGMs)., Methods: Diabetes Technology Society (DTS) convened 89 international experts in glucose monitoring to (1) smooth the borders of the Surveillance Error Grid (SEG) zones and create a user-friendly tool-the DTS Error Grid; (2) define five risk zones of clinical point accuracy (A-E) to be identical for BGMs and CGMs; (3) determine a relationship between DTS Error Grid percent in Zone A and mean absolute relative difference (MARD) from analyzing 22 BGM and nine CGM accuracy studies; and (4) create trend risk categories (1-5) for CGM trend accuracy., Results: The DTS Error Grid for point accuracy contains five risk zones (A-E) with straight-line borders that can be applied to both BGM and CGM accuracy data. In a data set combining point accuracy data from 18 BGMs, 2.6% of total data pairs equally moved from Zones A to B and vice versa (SEG compared with DTS Error Grid). For every 1% increase in percent data in Zone A, the MARD decreased by approximately 0.33%. We also created a DTS Trend Accuracy Matrix with five trend risk categories (1-5) for CGM-reported trend indicators compared with reference trends calculated from reference glucose., Conclusion: The DTS Error Grid combines contemporary clinician input regarding clinical point accuracy for BGMs and CGMs. The DTS Trend Accuracy Matrix assesses accuracy of CGM trend indicators., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: D.C.K. is a consultant for Afon, Lifecare, Novo, Samsung, embecta, Glucotrack, SynchNeuro, and Thirdwayv. G.F. is CEO of IfDT. G.F./IfDT has/have received research support, speakers’ honoraria or consulting fees in the last three years from Abbott, Ascensia, Berlin Chemie, Boydsense, Dexcom, Glucoset, i-SENS, Lilly, Menarini, Novo Nordisk, Perfood, Pharmasens, Roche, Sinocare, Terumo, Ypsomed. S.P. is an employee of IfDT. B.P.K. declares patent royalties handled by UVA from: DexCom, J&J, Novo Nordisk, and Sanofi; and research support handled by UVA: Dexcom, Novo Nordisk, Tandem Diabetes Care. D.K. has received research support from Abbott Diabetes Care. M.S.D.A. is currently receiving in kind support (CGM devices) from Dexcom Inc for an investigator-initiated clinical study. K.D. receives research funding from Dexcom, Abbott, Sanofi, Viacyte, Insulet, consulting fees from Eli Lilly, Dexcom, Insulet, Oppenheimer, Elsevier, honoraria from Academy for Continued Healthcare Learning, Med Learning Group, Medscape, Impact Education, and royalties from UptoDate. S.M. is in receipt of an investigator-initiated grant from DexCom, has received speaker fees from Sanofi & Lilly, is funded by a Wellcome Trust (223024/Z/21/Z), and is supported by the NIHR Imperial Biomedical Research Centre. A.S. was supported by the NSF Engineering Research Center for Precise Advanced Technologies and Health Systems for Underserved Populations (PATHS-UP) (#1648451). V.N.S. reports receiving personal fees from Sanofi, Embecta, NovoNordisk, Dexcom, Insulet, Tandem Diabetes Care, Ascensia Diabetes Care, Genomelink and LumosFit for consulting, advising or speaking. N.K.T. is a consultant for Roche Diagnostics / Roche Molecular Systems / Radiometer. UC Davis is a Roche Diagnostics Center of Excellence. N.K.T. has received speaking honoraria for Roche Diagnostics, Nova Biomedical, Thermo Fisher, and Radiometer. N.K.T. is also Chair-Elect for the Association for Diagnostic and Laboratory Medicine (ADLM) Critical and Point-of-Care Testing Division, Co-Founder of the Machine Intelligene Learning Optimizer (MILO), Inc, and a member of the International Federation for Clinical Chemistry (IFCC) continuous glucose monitoring workgroup. T.T. is a consultant for Clinical ink. R.E.A. is a consultant for Clinical ink. D.T.A. has received speaker’s honoraria from Abbott, Ascensia Diabetes Care, Insulet, Lilly Diabetes, Mannkind, Novo Nordisk, and Xeris Pharmaceuticals. D.T.A. has received consulting fees from Ascensia Diabetes Care, Lilly Diabetes, and Senseonics. H.K.A. received research grants through University of Colorado from Dexcom, Tandem Diabetes, Medtronic, Mannkind, IM Therapeutics, IAFMS, and received honorarium through University of Colorado for consulting from Dexcom, Tandem Diabetes, and Medtronic. M.E.A.-S. has served on the advisory boards for Abbott, Medtronic, Insulet, VitalAire, Sanofi, Eli Lilly, and Dexcom; has received honoraria for speaking from Abbott, Eli Lilly, Medtronic, Novo Nordisk, Sanofi, VitalAire, and Eli Lilly; and received research support from Medtronic and Sanofi. T.S.B. has received research support from Abbott Rapid Diagnostics, Biolinq, Dexcom, Eli Lilly, Medtronic, Medtrum, Novo Nordisk, Sanofi, Senseonics, and vTv Therapeutics and consulting honoraria from Abbott Diabetes, Abbott Rapid Diagnostics, ACON, CeQur, HagarTech, Intuity Medical, Lifescan, Mannkind, Medtronic, Novo, Perspirion, Sanofi, Sequel Med Tech, and Ypsomed. M.B. currently participates on the Hospital Advisory board with Dexcom and has received research support from Dexcom. L.B. has received research/product support from Dexcom, Ypsomed, and Boehringer Ingelheim; speaker honoraria from Dexcom and Oviva; and participated in advisory boards of Dexcom, Novo Nordisk, Sanofi, Ypsomed, Oviva, and Roche Diabetes Care. Y.M.B. has received honoraria for lectures and scientific advisory from Roche and AstraZeneca in the past 12 months. J.E.B. is on the Speaker’s bureau for Insulet and on the Advisory Board for Cardinal Health and Lifescan. J.E.B. is a consultant for Embecta. J.E.B. receives research support from the Leona M. and Harry B. Helmsley Charitable Trust. E.C. is on the scientific advisory board for Novo Nordisk, Eli-Lilly, Adocia, Arecor, Proventionbio, Portal Insulin, and MannKind. D.C. was a Dexcom employee from August 2018 to May 2024. D.C. is a shareholder of Dexcom, Lilly, Abbott and Tandem. M.C. has received consulting fees from Glooko and research support from Dexcom and Abbott Diabetes Care. G.L.C. is a shareholder of BioTex, Inc., Basepair Biotechnologies Inc., Coordination Centric, Inc., and Shape Memory Medical, Inc. G.L.C. is supported by the NSF Engineering Research Center for Precise Advanced Technologies and Health Systems for Underserved Populations (PATHS-UP) (#1648451). K.K.D. has received honoraria, travel, or fees for advisory boards from AstraZeneca, Novo Nordisk, Boehringer Ingelheim, Eli Lilly, Abbott Diabetes, Menarini, and Sanofi in the last 12 months. J.E. receives federal funding from FDA, NIMHD, and NCATS and is a consultant for Sanofi. C.F. receives royalties from Dexcom and Novo Nordisk managed through her institution. G.A.F. is an advisor for 180 Life Sciences, 89bio, Adocia, Abbott, AdipoPharma, Aerami, Amolyt, Carthera, Catalyst, Cohen Global, CMC Magnetics, Diasome, Eleos, Entera Bio, Enterin, Glyscend, Hagar, Hogan Lovells, IM Therapeutics, Innoneo, Intarcia, Levicure, Lilly Asia Ventures, Lumos, Mars Symbioscience, Melior, metaLead Therapeutics, Microbiotix, MMD, Modular Medical, New Amsterdam, Northwestern, NuSirt, NuVox, Oramed, Pano, Pasithea, PhylloPharma, Pleiogenix, Recordati, Regor, Remodeless, Renaissance, RenovoRx, Rivus, RxMP, Sera Biopharma, Seraxis, Serpin, SFC Fluidics, Skinject, SROne, Stalicla, Surf Bio, TIXiMED, Veroscience, Verthermia, WaveBreak, Zealand Pharma, and Zucara. M.A.L.G. is a consultant for Abbott, Medtronic, Novonordisk, and Roche. R.J.G. received research support from Novo Nordisk, Dexcom and Eli Lilly and consulting fees/advisory fees from Abbott Diabetes Care, Aztra Zeneca, Bayer, Boehringer, Dexcom, Eli Lilly, Novo Nordisk, and Medtronic, outside of this work. R.J.G. is partially supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Numbers P30DK111024, K23DK123384, R03DK138255, and U2CD137135. A.M.G.-M. reports speaker fees from Novo Nordisk, Sanofi, Elli Lilly, Boehringer Ingelheim, Abbott, and Medtronic. L.H. is a consultant for a number of companies that are developing innovative solutions for the treatment of people with diabetes. N.H. reports Advisory Board member fees from Abbott Diabetes Care and Insulet as well as honoraria for lectures from Berlin-Chemie AG, Becton Dickenson, Sanofi Germany, Roche Diabetes Care, and Dexcom Germany. T.H. serves on the advisory board for Acella and Horizons Therapeutics (no financial compensation). S.H. has served on the advisory board for Tandem, Dexcom, and Medtronic, and received honoraria for nonpromotional educational and/or consultancy work from Abbott, Insulet, Dexcom, Roche, and Sanofi. P.G.J. is a shareholder of Pacific Diabetes Technologies Inc. and serves on the advisory board for Eli Lilly. P.G.J. received grant support from SFC Fluidics and research support from Eli Lilly and Dexcom. J.J. has received fees from lectures and or advisory boards from Abbott, Astra Zeneca, Boeringer Ingelheim, Eli Lilly, Medtronic, Nordic Infucare, Novo Nordisk, and Sanofi. S.R.J is a consultant for USV, Marico, Glenmark, Franco Indian, Twin Health, Biocon, and Zydus Lifesciences. S.R.J. received speaking honoraria from Abbott, Novo Nordisk, MSD, Sanofi, Boehringer Ingelheim, AstraZeneca, Lupin, Bayer Zydus, USV, DRL, Meyer Organics, Servier, Natco. R.A.L. is a consultant for Abbott Diabetes Care, Biolinq, Capillary Biomedical, Deep Valley Labs, Gluroo, PhysioLogic Devices, Portal Insulin, Sanofi, and Tidepool. R.A.L. has served on advisory boards for. ProventionBio and Lilly. R.A.L. receives research support through his institution from Insulet, Medtronic, Tandem, and Sinocare. L.A.L. has received research funding from, has provided CME on behalf of, and/or has acted as an advisor to Abbott, AstraZeneca, Boehringer Ingelheim, Eli Lilly, Lexicon, Merck, Novo Nordisk, Pfizer, and Sanofi. M.L. has been a consultant or received honoraria from Astra Zeneca, Boehringer Ingelheim, Eli Lilly, Nordic InfuCare, and Novo Nordisk, and has received research grants from Eli Lilly and Novo Nordisk, all outside of the submitted work. J.K.M. is a member of advisory boards of Abbott Diabetes Care, Becton-Dickinson, Biomea Fusion, Eli Lilly, Embecta, Medtronic, NovoNordisk A/S, Roche Diabetes Care, Sanofi-Aventis, and Viatris and received speaker honoraria from A. Menarini Diagnostics, Abbott Diabetes Care, AstraZeneca, Boehringer Ingelheim, Dexcom, Eli Lilly, Medtrust, MSD, NovoNordisk A/S, Roche Diabetes Care, Sanofi, Viatris, and Ypsomed. J.K.M. is a shareholder of decide Clinical Software GmbH and elyte Diagnostics. A.M. reports speaker fees from Novo Nordisk. M.M. has an existing research & development relationship with Scientific Bioprocessing, Inc and has been a consultant for Abbott. S.-J.M. is a consultant for Abbott, Curestream, Daewoong, EOFlow, G2e, Huons, iSense, Medtronic, Novo Nordisk, and Sanofi. D.N.O. has served on advisory boards for Abbott Laboratories, Medtronic, Merck Sharp & Dohme, Novo Nordisk, Roche, and Sanofi; received research support from Medtronic, Novo Nordisk, Roche, Eli Lilly and Company, and Sanofi; and received travel support from Novo Nordisk and Merck Sharp & Dohme. F.J.P. has received research support (to Emory University) from Dexcom, Insulet, Novo Nordisk, Tandem, and Ideal Medical Technologies, and has received consulting fees from Dexcom. A.L.P. is on the advisory board of Medscape, Vertex, and Lilly; receives research support from Insulin and Abbott; and has stock options in Omada Health. R.P.-B. receives grant support from Novo Nordisk, Lexicon Pharmaceuticals, and Medtronic and received consulting fees from Bayer, Lexicon Pharmaceuticals, Novo Nordisk, and Roche. C.M.R. has received honoraria and/or grant support from AstraZeneca, Dexcom, Fresenius, and Vifor. D.B.S. is supported by the Intramural Research Program of the National Institutes of Health. S.S. was a Novo Nordisk employee from 2022-2023. S.S. has served as advisor for Novo Nordisk and has received speaker fees from Novo Nordisk and Nordic Infucare within the past three years. G.D.S’s employer, nonprofit International Diabetes Center, HealthPartners Institute, has received educational grant funds from Abbott Diabetes Care, Medscape, and Sanofi-Aventis Groupe. G.D.S receives no personal income/honorarium from these activities. K.S. received grant supports from Arkray, Terumo, and Dexcom. E.K.S. is partly supported by the VA Merit Award (1I01CX001825) from the US Department of Veterans Affairs Clinical Sciences Research and has received unrestricted research support from Dexcom and Tandem Diabetes (to Baltimore VA Medical Center and to University of Maryland) for the conduction of clinical trials. N.L.S. received funding from Novo Nordisk for an investigator-initiated research grant unrelated to the current project. G.E.U. is partly supported by research grants from National Institutes of Health (NIH/NATS UL 3UL1TR002378-05S2) from the Clinical and Translational Science Award program, and from National Institutes of Health and National Center for Research Resources (NIH/NIDDK 2P30DK111024-06). G.E.U. has received research support (to Emory University) from Abbott, Bayer, and Dexcom; and has participated in advisory boards for Dexcom and GlyCare. E.W. has received consulting fees from Abbott Diabetes Care, Ascensia, Bayer, Boehringer, Ingelheim, Embecta, GlaxoSmithKline, Lilly, Medtronic, Renalytix, and Sanofi. E.W. has received honoraria from Abbott Diabetes Care, Bayer, Boehringer Ingelheim, GlaxoSmithKline, Lilly, Medtronic, Renalytix, and Sanofi. E.W. is on the Speakers’ Bureau from Abbott Diabetes Care, Bayer, Boehringer, Ingelheim, GlaxoSmithKline, Lilly, Renalytix, and Sanofi. M.Z. is a consultant for DexCom, Inc. M.A.K. is Chief Medical Officer of QuesGen, Inc. C.T., C.L., B.V.H., J.S.K., W.A.L., S.Y.R., J.J.S., K.W., C.W., K.R., C.N.H., A.T.A., A.A., R.R.B., E.M.B., J.G.C., K.Y.C., A.D., N.E., S.K.K., U.M., N.M., C.M., J.H.N., A.P., P.R., S.M.S., B.S., M.V., H.W.V., J.W., A.H.B.W., and S.Y. have nothing to disclose.

Introduction: Internal standards correct for measurement variation due to sample loss. Isotope labeled analytes are ideal internal standards for the measurement of fatty acids in human plasma but are not always readily available. For this reason, quantification of multiple analytes at once is most often done using only a single or few internal standards. The magnitude of the impact this has on method accuracy and precision is not well studied for gas chromatography-mass spectrometry systems., Objective: This study aims to estimate bias and changes in uncertainty associated with using alternative fatty acid isotopologue internal standards for the estimation of similar or dissimilar long chain fatty acids., Method: Using a previously reported method for the quantification of 27 fatty acids in human plasma using 18 internal standards we obtained estimates of bias and uncertainty at up to three levels of fatty acid concentration., Results: With some notable exceptions, method accuracy remained relatively stable when using an alternative internal standard (Median Relative Absolute Percent Bias: 1.76%, Median Spike-Recovery Absolute Percent Bias: 8.82%), with larger changes in method precision (Median Increase in Variance: 141%). Additionally, the degree of difference between analyte and internal standard structure was related to the magnitude of bias and uncertainty of the measurement., Conclusion: The data presented here show that the choice of internal standard used to estimate fatty acid concentration can affect the accuracy and reliability of measurement results and, therefore, needs to be assessed carefully when developing analytical methods for the measurement of fatty acid profiles.Disclaimer: The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry. Use of trade names is for identification only and does not imply endorsement by the Centers for Disease Control and Prevention, the Public Health Service, and the US Department of Health and Human Services., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Background: The harmonization status of most tumor markers (TMs) is unknown. We report a feasibility study performed to determine whether external quality assessment (EQA) programs can be used to obtain insights into the current harmonization status of the tumor markers α-fetoprotein (AFP), prostate specific antigen (PSA), carcinoembryonic antigen (CEA), cancer antigen (CA)125, CA15-3 and CA19-9., Methods: EQA sample results provided by 6 EQA providers (INSTAND [Germany], Korean Association of External Quality Assessment Service [KEQAS, South Korea], National Center for Clinical Laboratories [NCCL, China], United Kingdom National External Quality Assessment Service [UK NEQAS, United Kingdom], Stichting Kwaliteitsbewaking Medische Laboratoriumdiagnostiek [SKML, the Netherlands], and the Royal College of Pathologists of Australasia Quality Assurance Programs [RCPAQAP, Australia]) between 2020 and 2021 were used. The consensus means, calculated from the measurement procedures present in all EQA programs (Abbott Alinity, Beckman Coulter DxI, Roche Cobas, and Siemens Atellica), was used as reference values. Per measurement procedure, the relative difference between consensus mean for each EQA sample and the mean of all patient-pool-based EQA samples were calculated and compared to minimum, desirable, and optimal allowable bias criteria based on biological variation., Results: Between 19040 (CA15-3) and 25398 (PSA) individual results and 56 (PSA) to 76 (AFP) unique EQA samples were included in the final analysis. The mean differences with the consensus mean of patient-pool-based EQA samples for all measurement procedures were within the optimum bias criterion for AFP, the desirable bias for PSA, and the minimum bias criterion for CEA. However, CEA results <8 µg/L exceeded the minimum bias criterion. For CA125, CA15-3, and CA19-9, the harmonization status was outside the minimum bias criterion, with systematic differences identified., Conclusions: This study provides relevant information about the current harmonization status of 6 tumor markers. A pilot harmonization investigation for CEA, CA125, CA15-3, and CA19-9 would be desirable., (© Association for Diagnostics & Laboratory Medicine 2024. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Thyroid-stimulating hormone (TSH) is an important clinical marker in the diagnosis and management of thyroid disease. TSH measurements are reported in milli-International Units per Litre (mIU/L), traceable to a World Health Organisation (WHO) reference material. There is a wide variety of commercial immunoassays for TSH measurements available, which have historically been poorly harmonised due to a lack of commutability of the WHO reference materials with patient samples. This led to the recent development of a serum-based reference panel for TSH, traceable to the WHO reference material, available via the International Federation for Clinical Chemistry and Laboratory Medicine (IFCC), aimed at harmonisation of TSH immunoassays. This report describes recent developments in the TSH reference system, including establishment of the 4th WHO International Standard for TSH, and aims to clarify the relationship between the available reference materials and their intended uses. This 4th WHO IS is widely available and defines the unit of TSH activity, therefore its continued existence is of paramount importance, however it continues to show a lack of commutability with patient in many TSH immunoassays. This makes the C-STFT TSH panel, albeit available in restricted numbers, a critical resource to ensure better TSH assay harmonisation., (© 2024 the author(s), published by De Gruyter, Berlin/Boston.)

Background: Free thyroxine (FT4) measurement is one of the most requested tests in patient care for diagnosing and treating thyroid-related illnesses. Equilibrium dialysis (ED) is considered the "gold standard" for FT4 measurement; however, several factors have a profound effect on the reliability of FT4 assays and require special consideration., Methods: In the current study, we focused on evaluating critical factors that could contribute to reporting errors, such as adsorption of thyroxine (T4) to labware surfaces, stability of serum samples, stock solutions, and calibrator storage conditions, as well as the solvents used to prepare T4 solutions., Results: The adsorption of T4 in ethanolic solutions and dialysates to labware surfaces can be reduced with the careful selection of pipette tips, test tubes, and 96-well plates. Adding pH modifiers to neat T4 solutions can improve its stability. FT4 in serum samples remains stable after exposure to four freeze-thaw cycles, 5 °C for 18-20 h, or -70 °C for a minimum of three years., Conclusion: The presented study has demonstrated that the loss of analyte due to pre-analytical and analytical factors during operation of the FT4 reference measurement procedure (RMP) can be minimized by careful selection of all labware for sample preparation. It was found that the accuracy and imprecision of FT4 assays can be influenced by different types of dialysis devices, but acceptable alternatives to ED membranes were identified. This study demonstrates approaches to establish a FT4 method that is independent from specific suppliers and addresses critical pre-analytical and analytical factors important for FT4 measurements., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Background: Accurate and reliable measurement of human serum free thyroxine (FT4) is critical for the diagnosis and treatment of thyroid diseases. However, concerns have been raised regarding the performance of FT4 measurements in patient care. Centers for Disease Control and Prevention Clinical Standardization Programs (CDC-CSP) address these concerns by creating a FT4 standardization program to standardize FT4 measurements. The study aims to develop a highly accurate and precise candidate Reference Measurement Procedure (cRMP), as one key component of CDC-CSP, for standardization of FT4 measurements., Methods: Serum FT4 was separated from protein-bound thyroxine with equilibrium dialysis (ED) following the recommended conditions in the Clinical and Laboratory Standards Institute C45-A guideline and the published RMP [20,21,23]. FT4 in dialysate was directly quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS) without derivatization. Gravimetric measurements of specimens and calibrator solutions, calibrator bracketing, isotope dilution, enhanced chromatographic resolution, and T4 specific mass transitions were used to ensure the accuracy, precision, and specificity of the cRMP., Results: The described cRMP agreed well with the established RMP and two other cRMPs in an interlaboratory comparison study. The mean biases of each method to the overall laboratory mean were within ±2.5%. The intra-day, inter-day, and total imprecision for the cRMP were within 4.4%. The limit of detection was 0.90 pmol/L, which was sufficiently sensitive to determine FT4 for patients with hypothyroidism. The structural analogs of T4 and endogenous components in dialysate did not interfere with the measurements., Conclusion: Our ED-LC-MS/MS cRMP provides high accuracy, precision, specificity, and sensitivity for FT4 measurement. The cRMP can serve as a higher-order standard for establishing measurement traceability and provide an accuracy base for the standardization of FT4 assays., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Inc.)

Objectives: The clinical use of soluble transferrin receptor (sTfR) as an iron status indicator is hindered by a lack of assay standardization and common reference ranges and decision thresholds. In 2009, the WHO and National Institute for Biological Standards and Controls (NIBSC) released a sTfR reference material (RM), 07/202, for assay standardization; however, a comprehensive, formal commutability study was not conducted., Methods: This study evaluated the commutability of WHO 07/202 sTfR RM and human serum pools and the impacts of their use as common calibrators. Commutability was assessed for six different measurement procedures (MPs). Serum pools were prepared according to updated CLSI C37-A procedures (C37) or non-C37 procedures. The study design and analyses were based on Parts 2 and 3 of the 2018 IFCC Commutability in Metrological Traceability Working Group's Recommendations for Commutability Assessment. WHO 07/202 and serum pools were used for instrument/assay and mathematical recalibration, respectively, to determine if their use decreases inter-assay measurement variability for clinical samples., Results: The WHO 07/202 RM dilutions were commutable for all 6 MPs assessed and, when used for instrument calibration, decreased inter-assay variability from 208 to 55.7 %. Non-C37 and C37 serum pools were commutable for all 6 MPs assessed and decreased inter-assay variability from 208 to 13.8 % and 4.6 %, respectively, when used for mathematical recalibration., Conclusions: All materials evaluated, when used as common calibrators, substantially decreased inter-assay sTfR measurement variability. MP calibration to non-C37 and C37 serum pools may reduce the sTfR IMPBR to a greater extent than WHO 07/202 RM., (© 2023 the author(s), published by De Gruyter, Berlin/Boston.)

Objectives: Free thyroxine (FT4) in serum is routinely measured in clinical practice to diagnose and monitor thyroid disease. Due to its concentration in picomolar range and the delicate equilibrium of free and protein-bound T4, accurate measurement is challenging. As a consequence, large inter-method differences in FT4 results exists. Optimal method design and standardization of the FT4 measurement is therefore necessary. The IFCC Working Group for Standardization of Thyroid Function Tests proposed a reference system with a conventional reference measurement procedure (cRMP) for FT4 in serum. In this study, we describe our FT4 candidate cRMP and its validation in clinical samples., Methods: This candidate cRMP is based on equilibrium dialysis (ED) combined with determination of T4 with an isotope-dilution liquid chromatography tandem mass-spectrometry (ID-LC-MS/MS) procedure and was developed according to the endorsed conventions. Its accuracy, reliability, and comparability was investigated using human sera., Results: It was shown that the candidate cRMP adhered to the conventions and its accuracy, precision, and robustness were adequate in serum of healthy volunteers., Conclusions: Our candidate cRMP measures FT4 accurately and performs well in serum matrix., (© 2023 the author(s), published by De Gruyter, Berlin/Boston.)

Background: Elevated concentrations of lipoprotein(a) [Lp(a)] are directly related to an increased risk of cardiovascular diseases, making it a relevant biomarker for clinical risk assessment. However, the lack of global standardization of current Lp(a) measurement procedures (MPs) leads to inconsistent patient care. The International Federation for Clinical Chemistry and Laboratory Medicine working group on quantitating apolipoproteins by mass spectrometry (MS) aims to develop a next-generation SI (International system of units)-traceable reference measurement system consisting of a MS-based, peptide-calibrated reference measurement procedure (RMP) and secondary serum-based reference materials (RMs) certified for their apolipoprotein(a) [apo(a)] content. To reach measurement standardization through this new measurement system, 2 essential requirements need to be fulfilled: a sufficient correlation among the MPs and appropriate commutability of future serum-based RMs., Methods: The correlation among the candidate RMP (cRMP) and immunoassay-based MPs was assessed by measuring a panel of 39 clinical samples (CS). In addition, the commutability of 14 different candidate RMs was investigated., Results: Results of the immunoassay-based MPs and the cRMPs demonstrated good linear correlations for the CS but some significant sample-specific differences were also observed. The results of the commutability study show that RMs based on unspiked human serum pools can be commutable with CS, whereas human pools spiked with recombinant apo(a) show different behavior compared to CS., Conclusions: The results of this study show that unspiked human serum pools are the preferred candidate secondary RMs in the future SI-traceable Lp(a) Reference Measurement System., (© American Association for Clinical Chemistry 2023.)

Background: Medical results generated by European CE Marking for In Vitro Diagnostic or in-house tests should be traceable to higher order reference measurement systems (RMS), such as International Federation of Clinical Chemistry and Laboratory Medicine (IFCC)-endorsed reference measurement procedures (RMPs) and reference materials. Currently, serum apolipoprotein (a) [apo(a)] is recognized as a novel risk factor for cardiovascular risk assessment and patient management. The former RMS for serum apo(a) is no longer available; consequently, an International System of Units (SI)-traceable, ideally multiplexed, and sustainable RMS for apo(a) is needed., Methods: A mass spectrometry (MS)-based candidate RMP (cRMP) for apo(a) was developed using quantitative bottom-up proteomics targeting 3 proteotypic peptides. The method was provisionally validated according to ISO 15193 using a single human serum based calibrator traceable to the former WHO-IFCC RMS., Results: The quantitation of serum apo(a) was by design independent of its size polymorphism, was linear from 3.8 to 456 nmol/L, and had a lower limit of quantitation for apo(a) of 3.8 nmol/L using peptide LFLEPTQADIALLK. Interpeptide agreement showed Pearson Rs of 0.987 and 0.984 for peptides GISSTVTGR and TPENYPNAGLTR, and method comparison indicated good correspondence (slopes 0.977, 1.033, and 1.085 for LFLEPTQADIALLK, GISSTVTGR, and TPENYPNAGLTR). Average within-laboratory imprecision of the cRMP was 8.9%, 11.9%, and 12.8% for the 3 peptides., Conclusions: A robust, antibody-independent, MS-based cRMP was developed as higher order RMP and an essential part of the apo(a) traceability chain and future RMS. The cRMP fulfils predefined analytical performance specifications, making it a promising RMP candidate in an SI-traceable MS-based RMS for apo(a)., (©American Association for Clinical Chemistry 2023.)

Competing Interests: Authors’ Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest:

Full-length parathyroid hormone (PTH 1-84) is crucial for the regulation of calcium and phosphate homeostasis and bone remodeling. PTH 1-84 is metabolized into various PTH fragments, which are measured with varying levels of efficiency by PTH immunoassays. These PTH fragments, which increase in serum as CKD progresses, could potentially modulate the effects of PTH 1-84 and contribute to CKD-associated bone disorders. To obtain a true biologic representation of total PTH bioactivity, it is necessary to measure not only PTH 1-84 but also PTH fragments that are present in circulation. Traditional second-generation PTH immunoassays collectively measure PTH 1-84, PTH fragments, and post-translationally modified PTH 1-84, making it difficult to accurately predict the character of underlying renal osteodystrophy. This review highlights current advances in methods available for PTH measurement and the clinical relevance of PTH fragments in CKD. We emphasize the usefulness of mass spectrometry as a potential reference method for PTH measurement., (Copyright © 2022 by the American Society of Nephrology.)

Importance: Appropriately established pediatric reference intervals are critical to the clinical decision-making process and should reflect the physiologic changes that occur during healthy child development. Reference intervals used in pediatric care today remain highly inconsistent across a broad range of common clinical biomarkers., Observations: This narrative review assesses biomarker-specific pediatric reference intervals and their clinical utility with respect to the underlying biological changes occurring during development. Pediatric reference intervals from PubMed-indexed articles published from January 2015 to April 2021, commercial laboratory websites, study cohorts, and pediatric reference interval books were all examined. Although large numbers of pediatric reference intervals are published for some biomarkers, very few are used by clinical and commercial laboratories. The patterns, extent, and timing of biomarker changes are highly variable, particularly during developmental stages with rapid physiologic changes. However, many pediatric reference intervals do not capture these changes and thus do not accurately reflect the underlying biochemistry of development, resulting in significant inconsistencies between reference intervals., Conclusions and Relevance: There is a need to correctly describe the biochemistry of child development as well as to identify strategies to develop accurate and consistent pediatric reference intervals for improved pediatric care.

Background: The JCTLM created a Task Force on Reference Measurement System Implementation (TF-RMSI) to provide guidance on metrological traceability implementation for the in vitro diagnostics (IVD) community., Content: TF-RMSI investigated the reference measurement systems (RMS) for 13 common measurands by applying the following procedural steps: (a) extracting data from the JCTLM database of available certified reference materials (CRMs) and reference measurement procedures (RMPs); (b) describing the RMS to which each recruited CRM or RMP belongs; (c) identifying the intended use of the CRMs, and, if used as a common calibrator for IVD measuring systems and/or trueness assessment of field methods was included, checking the CRM's certificate for information about commutability with clinical samples; and (d) checking if the CRM or RMP measurement uncertainty (MU) has the potential to be small enough to avoid significantly affecting the analytical performance specifications (APS) for MU of clinical sample results when the MU from the IVD calibrator and from the end-user measuring system were combined., Summary: We produced a synopsis of JCTLM-listed higher-order CRMs and RMPs for the selected measurands, including their main characteristics for implementing traceability and fulfilling (or not) the APS for suitable MU. Results showed that traceability to higher-order references can be established by IVD manufacturers within the defined APS for most of the 13 selected measurands. However, some measurands do not yet have suitable CRMs for use as common calibrators. For these measurands, splitting clinical samples with a laboratory performing the RMP may provide a practical alternative for establishing a calibration hierarchy., (© American Association for Clinical Chemistry 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Former smokers who currently use e-cigarettes have lower concentrations of biomarkers of tobacco toxicant exposure than current smokers. It is unclear whether tobacco toxicant exposure reductions may lead to health risk reductions., Methods: We compared inflammatory biomarkers (high-sensitivity C-reactive protein, IL6, fibrinogen, soluble intercellular adhesion molecule-1) and an oxidative stress marker (F2-isoprostane) among 3,712 adult participants in Wave 1 (2013-2014) of the Population Assessment of Tobacco and Health Study by tobacco user groups: dual users of cigarettes and e-cigarettes; former smokers who currently use e-cigarettes-only; current cigarette-only smokers; former smokers who do not currently use any tobacco; and never tobacco users. We calculated geometric means (GM) and estimated adjusted GM ratios (GMR)., Results: Dual users experienced greater concentration of F2-isoprostane than current cigarette-only smokers [GMR 1.09 (95% confidence interval, CI, 1.03-1.15)]. Biomarkers were similar between former smokers who currently use e-cigarettes and both former smokers who do not use any tobacco and never tobacco users, but among these groups most biomarkers were lower than those of current cigarette-only smokers. The concentration of F2-isoprostane decreased by time since smoking cessation among both exclusive e-cigarette users ( P trend = 0.03) and former smokers who do not currently use any tobacco ( P trend = 0.0001)., Conclusions: Dual users have greater concentration of F2-isoprostane than smokers. Exclusive e-cigarette users have biomarker concentrations that are similar to those of former smokers who do not currently use tobacco, and lower than those of exclusive cigarette smokers., Impact: This study contributes to an understanding of the health effects of e-cigarettes., (©2021 American Association for Cancer Research.)

Lipoprotein measurements are pivotal in the management of patients at risk for atherosclerotic coronary heart disease (CHD) with myocardial infarction and coronary death as the main outcomes, and for atherosclerotic cardiovascular disease (ASCVD), which includes CHD and stroke. Recent developments and changes in guidelines affect optimization of using lipid measures as cardiovascular biomarkers. This scientific statement reviews the pre-analytical, analytical, post-analytical, and clinical aspects of lipoprotein measurements. Highlights include the following: i) It is acceptable to screen with nonfasting lipids. ii) non-high-density lipoprotein HDL-cholesterol (non-HDL-C) is measured reliably in either the fasting or the nonfasting state and can effectively guide ASCVD prevention. iii) low density lipoprotein cholesterol (LDL-C) can be estimated from total cholesterol, high density lipoprotein cholesterol (HDL-C), and triglyceride (TG) measurements. For patients with LDL-C>100 mg/dL and TG ≤150 mg/dL it is reasonable to use the Friedewald formula. However, for those with TG 150-400 mg/dL the Friedewald formula for LDL-C estimation is less accurate. The Martin/Hopkins method is recommended for LDL-C estimation throughout the range of LDL-C levels and up to TG levels of 399 mg/dL. For TG levels ≥400 mg/dL LDL-C estimating equations are currently not recommended and newer methods are being evaluated. iv) When LDL-C or TG screening results are abnormal the clinician should consider obtaining fasting lipids. v) Advanced lipoprotein tests using apolipoprotein B (apoB), LDL Particle Number (LDL-P) or remnant cholesterol may help to guide therapeutic decisions in select patients, but data are limited for patients already on lipid lowering therapy with low LDL-C levels. Better harmonization of advanced lipid measurement methods is needed. Lipid measurements are recommended 4-12 weeks after a change in lipid treatment. Lipid laboratory reports should denote desirable values and specifically identify extremely elevated LDL-C levels (≥190 mg/dL at any age or ≥160 mg/dL in children) as severe hypercholesterolemia. Potentially actionable abnormal lipid test results, including fasting triglycerides (TG) ≥500 mg/dL, should be reported as hypertriglyceridemia. Appropriate use and reporting of lipid tests should improve their utility in the management of persons at high risk for ASCVD events., (Copyright © 2021. Published by Elsevier Inc.)

Context: Soy formula feeding is common in infancy and is a source of high exposure to phytoestrogens, documented to influence vaginal cytology in female infants. Its influence on minipuberty in males has not been established., Objective: To assess the association between infant feeding practice and longitudinally measured reproductive hormones and hormone-responsive tissues in infant boys., Methods: The Infant Feeding and Early Development study was a prospective cohort of maternal-infant dyads requiring exclusive soy formula, cow milk formula, or breast milk feeding during study follow-up. In the 147 infant boy participants, serum testosterone, luteinizing hormone, stretched penile length, anogenital distance, and testis volume were longitudinally assessed from birth to 28 weeks. We examined feeding-group differences in age trajectories for these outcomes using mixed-effects regression splines., Results: Median serum testosterone was at pubertal levels at 2 weeks (176 ng/dL [quartiles: 124, 232]) and remained in this range until 12 weeks in all feeding groups. We did not observe differences in trajectories of hormone concentrations or anatomical measures between boys fed soy formula (n = 55) and boys fed cow milk formula (n = 54). Compared with breastfed boys (n = 38), soy formula-fed boys had a more rapid increase in penile length (P = .004) and slower initial lengthening of anogenital distance (P = .03), but no differences in hormone trajectories., Conclusion: Reproductive hormone concentrations and anatomical responses followed similar trajectories in soy and cow milk formula-fed infant boys. Our findings suggest that these measures of early male reproductive development do not respond to phytoestrogen exposure during infancy., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Measurements of thyroid stimulating hormone (TSH) and free thyroxine (fT4) are critical for the early detection of thyroid diseases and for monitoring treatment. The IFCC Committee for Standardization of Thyroid Function Tests (C-STFT) established reference systems for TSH harmonization and FT4 standardization, and is now working national partners on implementing these reference systems. These implementation activities include the maintenance of the reference systems, their use to standardize and harmonize assays, and educational activities to inform stakeholders about anticipated changes in measurement values as a result of standardization and harmonization. The IFCC C-STFT formed a network of reference laboratories for FT4 and is creating a new harmonization panel for TSH. The U.S. Centers for Disease Control and Prevention is a member of the reference laboratory network and is launching a formal standardization program for FT4. In Japan, national organizations successfully implemented TSH harmonization and established harmonized reference intervals for TSH. The C-STFT made available on its website research findings about potential concerns, communication needs and benefits of FT4 standardization and is assisting local organizations with communicating changes related to these standardization and harmonization efforts. Implementation of fT4 standardization and TSH harmonization is a complex, continuous task that requires collaboration with IVD manufacturers, laboratories, physicians and health care providers. C-STFT is working successfully with national organizations and local groups on improving FT4 and TSH measurements., (Published by Elsevier B.V.)

Background: The precise concentrations of full-length parathyroid hormone (PTH1-84) and the identity and concentrations of PTH fragments in patients with various stages of chronic renal failure are unknown., Methods: We developed a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method to characterize and quantify PTH1-84 and PTH fragments in serum of 221 patients with progressive renal dysfunction. Following capture by matrix-bound amino-terminal or carboxyl-terminal region-specific antibodies and elution from matrix, PTH1-84 and PTH fragments were identified and quantitated using LC-HRMS. PTH was simultaneously measured using an intact PTH (iPTH) immunoassay., Results: Full-length PTH1-84 and 8 PTH fragments (PTH28-84, 34-77, 34-84, 37-77, 37-84, 38-77, 38-84, and 45-84) were unequivocally identified and were shown to increase significantly when an eGFR declined to ≤17-23 mL/min/1.73m2. Serum concentrations of PTH1-84 were similar when measured by LC-HRMS following capture by amino-terminal or carboxyl-terminal immunocapture methods. In patients with an eGFR of <30 mL/min/1.73 m2, serum PTH concentrations measured using LC-HRMS were significantly lower than PTH measured using an iPTH immunoassay. PTH7-84 and oxidized forms of PTH1-84 were below the limit of detection (30 and 50 pg/mL, respectively)., Conclusions: LC-HRMS identifies circulating PTH1-84, carboxyl-terminal PTH fragments, and mid-region PTH fragments, in patients with progressive renal failure. Serum PTH1-84 and its fragments markedly rise when an eGFR decreases to ≤17-23 mL/min/1.73 m2. PTH concentrations measured using LC-HRMS tend to be lower than those measured using an iPTH immunoassay, particularly in severe chronic renal failure. Our data do not support the existence of circulating PTH7-84 and oxidized PTH1-84., (© American Association for Clinical Chemistry 2021.)

Context: Epidemiologic studies have demonstrated that overweight/obese girls (OW/OB) undergo thelarche and menarche earlier than normal weight girls (NW). There have been no longitudinal studies to specifically investigate how body weight/fat affects both clinical and biochemical pubertal markers in girls., Objective: To investigate the effect of total body fat on reproductive hormones and on the maturation of estrogen-sensitive tissues during puberty in girls., Methods: Ninety girls (36 OW/OB, 54 NW), aged 8.2 to 14.7 years, completed 2.8 ± 1.7 study visits over 4 years. Visits included dual-energy x-ray absorptiometry to calculate total body fat (TBF), Tanner staging, breast ultrasound for morphological staging (BMORPH; A-E), pelvic ultrasound, hormone tests, and assessment of menarchal status. The effect of TBF on pubertal markers was determined using a mixed, multistate, or Cox proportional hazards model, controlling for baseline BMORPH., Results: NW were older than OW/OB (11.3 vs 10.2 years, P < .01) at baseline and had more advanced BMORPH (P < .01). Luteinizing hormone, estradiol, and ovarian and uterine volumes increased with time with no effect of TBF. There was a time × TBF interaction for follicle-stimulating hormone, inhibin B, estrone, total and free testosterone, and androstenedione: Levels were initially similar, but after 1 year, levels increased in girls with higher TBF, plateaued in girls with midrange TBF, and decreased in girls with lower TBF. Girls with higher TBF progressed through BMORPH stage D more slowly but achieved menarche earlier than girls with lower TBF., Conclusion: In late puberty, girls with higher TBF demonstrate differences in standard hormonal and clinical markers of puberty. Investigation of the underlying causes and clinical consequences of these differences in girls with higher TBF deserves further study., (Published by Oxford University Press on behalf of the Endocrine Society 2021.)

Background: Intake of trans fatty acids (TFAs) increases LDL cholesterol, decreases HDL cholesterol, and increases the risk of heart disease morbidity and mortality. Many food products potentially contain industrially produced or ruminant TFAs. However, little is known about the dietary sources of plasma TFA concentrations., Objective: The objective of this study was to examine associations between foods consumed and plasma TFA concentrations using 24-h dietary recall data and plasma TFA measures among adults aged ≥20 y who participated in the NHANES 2009-2010 in the United States., Methods: Over 4400 food products in the dietary interview data were categorized into 32 food and beverage groups/subgroups. Four major plasma TFAs (palmitelaidic acid, elaidic acid, vaccenic acid, linolelaidic acid) and the sum of the 4 TFAs (sumTFAs) were analyzed using GC-MS. Multivariable linear regression analyses were conducted to identify associations of plasma TFAs with all 32 food and beverage groups/subgroups, controlling for the potential confounding effects of 11 demographic, socioeconomic, behavioral, lifestyle, and health-related variables., Results: Consumption of the following food groups/subgroups was significantly associated with elevated plasma TFA concentrations: cream substitutes ( P  < 0.001 for palmitelaidic acid, elaidic acid, vaccenic acid, and sumTFAs); cakes, cookies, pastries, and pies ( P  < 0.001 for elaidic acid, vaccenic acid, and sumTFAs; P  < 0.05 for linolelaidic acid); milk and milk desserts ( P  < 0.01 for palmitelaidic acid and vaccenic acid; P  < 0.05 for linolelaidic acid and sumTFAs); beef/veal, lamb/goat, and venison/deer ( P  < 0.01 for vaccenic acid; P  < 0.05 for sumTFAs); and butters ( P  < 0.001 for palmitelaidic acid and vaccenic acid; P  < 0.05 for sumTFAs)., Conclusions: The findings suggest that the above 5 food groups/subgroups could be the main dietary sources of plasma TFAs among adults in the United States in 2009-2010., (Published by Oxford University Press on behalf of the American Society for Nutrition 2021.)

Background: Up to now, 3 epidemiological studies have shown clear inverse associations between prenatal acrylamide exposure and birth size. In addition to studying the association between acrylamide and birth size, we investigated the interaction between acrylamide and polymorphisms in acrylamide-metabolising genes, with the aim of probing the causality of the inverse relationship between acrylamide and fetal growth., Methods: We investigated the association between prenatal acrylamide exposure (acrylamide and glycidamide hemoglobin adduct levels (AA-Hb and GA-Hb) in cord blood) and birth weight, length and head circumference in 443 newborns of the ENVIRONAGE (ENVIRonmental influence ON AGEing in early life) birth cohort. In addition, we studied interaction with single nucleotide polymorphisms (SNPs) in CYP2E1, EPHX1 and GSTP1, using multiple linear regression analysis., Results: Among all neonates, the body weight, length and head circumference of neonates in the highest quartile was - 101 g (95% CI: - 208, 7; p for trend = 0.12), - 0.13 cm (95% CI: - 0.62, 0.36; p for trend = 0.69) and - 0.41 cm (- 0.80, - 0.01; p for trend = 0.06) lower, respectively, compared to neonates in the lowest quartile of AA-Hb in cord blood, For GA-Hb, the corresponding effect estimates were - 222 g (95% CI: - 337, - 108; p for trend = 0.001), - 0.85 (95% CI: - 1.38, - 0.33; p for trend = 0.02) and - 0.55 (95% CI: - 0.98, - 0.11; p for trend = 0.01), respectively. The associations for GA-Hb were similar or stronger in newborns of non-smoking mothers. There was no statistically significant interaction between acrylamide exposure and the studied genetic variations but there was a trend of stronger inverse associations with birth weight and head circumference among newborns with homozygous wildtypes alleles for the CYP2E1 SNPS and with variant alleles for a GSTP1 SNP (rs1138272)., Conclusions: Prenatal dietary acrylamide exposure, specifically in the form of its metabolite glycidamide, was inversely associated with birth weight, length and head circumference. The interaction pattern with SNPs in CYP2E1, although not statistically significant, is an indication for the causality of this association. Other studies are needed to corroborate this finding.

Current dyslipidemia management in patients with atherosclerotic cardiovascular disease (ASCVD) is based on traditional serum lipids. Yet, there is some indication from basic research that serum apolipoproteins A-I, (a), B, C-I, C-II, C-III, and E may give better pathophysiological insight into the root causes of dyslipidemia. To facilitate the future adoption of clinical serum apolipoprotein (apo) profiling for precision medicine, strategies for accurate testing should be developed in advance. Recent discoveries in basic science and translational medicine set the stage for the IFCC Working Group on Apolipoproteins by Mass Spectrometry. Main drivers were the convergence of unmet clinical needs in cardiovascular disease (CVD) patients with enabling technology and metrology. First, the residual cardiovascular risk after accounting for established risk factors demonstrates that the current lipid panel is too limited to capture the full complexity of lipid metabolism in patients. Second, there is a need for accurate test results in highly polymorphic and atherogenic apolipoproteins such as apo(a). Third, sufficient robustness of mass spectrometry technology allows reproducible protein quantification at the molecular level. Fourth, several calibration hierarchies in the revised ISO 17511:2020 guideline facilitate metrological traceability of test results, the highest achievable standard being traceability to SI. This article outlines the conceptual approach aimed at achieving a novel, multiplexed Reference Measurement System (RMS) for seven apolipoproteins based on isotope dilution mass spectrometry and peptide-based calibration. This RMS should enable standardization of existing and emerging apolipoprotein assays to SI, within allowable limits of measurement uncertainty, through a sustainable network of Reference Laboratories., (© American Association for Clinical Chemistry 2020.)

Currently the 25-hydroxy vitamin D (25(OH)D) concentration is thought to be the best estimate of the vitamin D status of an individual. Unfortunately, its measurement remains complex, despite recent technological advances. We evaluated the biological variation (BV) of 25(OH)D in order to set analytical performance specifications (APS) for measurement uncertainty (MU). Six European laboratories recruited 91 healthy participants. The 25(OH)D concentrations in K 3 -EDTA plasma were examined weekly for up to 10 weeks in duplicate on a Lumipulse G1200 (Fujirebio, Tokyo, Japan). The linear regression of the mean 25(OH)D concentrations at each blood collection showed that participants were not in a steady state. The dissection of the 10-sample collection into two subsets, namely collections 1-5 and 6-10, did not allow for correction of the lack of homogeneity: estimates of the within-subject BV ranged from 5.8% to 7.1% and the between-subject BV ranged from 25.0% to 39.2%. Methods that would differentiate a difference induced by 25(OH)D supplementation at p < 0.05 should have MU < 13.6%, while at p < 0.01, the MU should be <9.6%. The development of APS using BV assumes a steady state of patients. The findings in this study suggest that patients are not in steady state. Therefore, APS that are based on MU appear to be more appropriate.

Lipidomics is a rapidly growing field, fueled by developments in analytical instrumentation and bioinformatics. To date, most researchers and industries have employed their own lipidomics workflows without a consensus on best practices. Without a community-wide consensus on best practices for the prevention of lipid degradation and transformations through sample collection and analysis, it is difficult to assess the quality of lipidomics data and hence trust results. Clinical studies often rely on samples being stored for weeks or months until they are analyzed, but inappropriate sampling techniques, storage temperatures, and analytical protocols can result in the degradation of complex lipids and the generation of oxidized or hydrolyzed metabolite artifacts. While best practices for lipid stability are sample dependent, it is generally recommended that strategies during sample preparation capable of quenching enzymatic activity and preventing oxidation should be considered. In addition, after sample preparation, lipid extracts should be stored in organic solvents with antioxidants at -20 °C or lower in an airtight container without exposure to light or oxygen. This will reduce or eliminate sublimation, and chemically and physically induced molecular transformations such as oxidation, enzymatic transformation, and photon/heat-induced degradation. This review explores the available literature on lipid stability, with a particular focus on human health and/or clinical lipidomic applications. Specifically, this includes a description of known mechanisms of lipid degradation, strategies, and considerations for lipid storage, as well as current efforts for standardization and quality insurance of protocols., (© 2020 AOCS.)

A sensitive, selective, and quantitative method incorporating high-resolution mass spectrometry was developed for the determination of blood urea nitrogen (BUN) in bronchoalveolar lavage fluid. The method requires no sample cleanup or derivatization prior to analysis. High-performance liquid chromatography (HPLC) on a Hypersil Gold PFP column (100 × 3 mm, 3 μm particle size) connected to a C18 guard column was employed for a 10 min chromatographic separation. The detection of urea was achieved using a Thermo Scientific Q-Exactive Plus instrument incorporating selected ion monitoring (SIM) modes for the protonated adduct of urea. The urea analytical measuring range for the method is 0.047-17.134 mg/dL, resulting in a BUN analytical measurement range of 0.022-8.007 mg/dL, which allows for quantitation over 3 orders of magnitude ( R 2 = 0.999). In addition, the method is suitable for small sample volumes (15 μL) with a high level of accuracy, precision, and specificity.

Manufacturers of in vitro diagnostic medical devices, clinical laboratories, research laboratories and calibration laboratories require commutable reference materials that can be used in the calibration hierarchies of medical laboratory measurement procedures used for human specimens to establish metrological traceability to higher order reference systems. Commutable materials are also useful in external quality assessment surveys. In order to achieve these goals, matrix-based reference materials with long-term stability, appropriate measurand concentrations and commutability with individual human specimens are required. The Clinical and Laboratory Standards Institute (CLSI) guideline C37-A (now archived) provided guidance to prepare commutable pooled serum reference materials for use in the calibration hierarchies of cholesterol measurement procedures. Experience using the C37-A guideline has identified a number of technical enhancements as well as applications to measurands other than cholesterol. This experience is incorporated into this updated protocol to ensure the procedure will continue to meet the needs of the medical laboratory. The updated protocol describes a procedure for preparing frozen human serum units or pools with minimal matrix alterations that are likely to be commutable with individual human serum samples. The protocol provides step-by-step guidance for the planning phase, collection of individual serum units, processing the units, qualifying the units for use in a pool and frozen storage of aliquots of pooled sera to manufacture frozen serum pools. Guidance on how to perform quality control of the final product and suggestions on documentation are also provided.

Trans-fatty acid (TFA) intake can increase the risk of coronary heart disease (CHD) morbidity and mortality and all-cause mortality. Industrially produced TFAs and ruminant TFAs are the major sources in foods. TFA intake and TFA-attributed CHD mortality vary widely worldwide. Excessive TFA intake is a health threat in high-income countries; however, it is also a threat in low- and middle-income countries (LMICs). Data on TFA intake are scarce in many LMICs and an urgent need exists to monitor TFAs globally. We reviewed global TFA intake and TFA-attributed CHD mortality and current progress toward policy or regulation on elimination of industrially produced TFAs in foods worldwide. Human biological tissues can be used as biomarkers of TFAs because they reflect actual intake from various foods. Measuring blood TFA levels is a direct and reliable method to quantify TFA intake.

Background: Girls who are overweight/obese (OB) develop breast tissue but do not undergo menarche (the first menstrual period) significantly earlier than girls of normal weight (NW). It has been proposed that estrogen synthesized by adipose tissue may be contributory, yet OB do not have higher serum estrogen levels than NW matched on breast stage. We hypothesized that estrogen synthesized locally, in mammary fat, may contribute to breast development. This hypothesis would predict that breast development would be more advanced than other estrogen-sensitive tissues as a function of obesity and body fat., Methods: Eighty premenarchal girls (26 OB, 54 NW), aged 8.2-14.7 years, underwent dual-energy x-ray absorptiometry to calculate percent body fat (%BF), Tanner staging of the breast, breast ultrasound for morphological staging, trans-abdominal pelvic ultrasound, hand x-ray (bone age, BA), a blood test for reproductive hormones, and urine collection to determine the vaginal maturation index (VMI), an index of estrogen exposure in urogenital epithelial cells., Results: When controlling for breast morphological stage determined by ultrasound, %BF was not associated with serum estrogen or gonadotropin (LH and FSH) levels or with indices of systemic estrogen action (uterine volume, endometrial thickness, BA advancement, and VMI). Tanner breast stage did not correlate with breast morphological stage and led to misclassification of chest fatty tissue as breast tissue in some OB., Conclusions: These studies do not support the hypothesis that estrogen derived from total body fat or local (mammary) fat contributes to breast development in OB girls.

Background: For optimal medical decision-making, harmonized reference intervals for estradiol for different ages and both sexes are needed. Our aim was to establish reference intervals using a highly accurate and traceable LC-MS/MS method and to compare these with reference intervals in literature., Methods: Estradiol was measured in serum obtained daily during the menstrual cycle of 30 healthy premenopausal women and in serum of 64 men and 33 postmenopausal women. The accuracy of our LC-MS/MS method was demonstrated by a method comparison with the CDC reference method., Results: Our LC-MS/MS method was traceable to the reference method. Estradiol reference interval during the early follicular phase (days -15 to -6) was 31-771 pmol/L; during the late follicular phase (days -5 to -1) 104-1742 pmol/L; during the LH peak (day 0) 275-2864 pmol/L; during the early luteal phase (days +1 to +4) 95-1188 pmol/L; during mid luteal phase (days +5 to +9) 151-1941 pmol/L; during late luteal phase (days +10 to +14) 39-1769 pmol/L. The reference interval for men was 12-136 pmol/L and for postmenopausal women <26 pmol/L., Conclusions: The established estradiol reference intervals can be used for all traceable LC-MS/MS methods for medical-decision making., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Objectives: To estimate the impact of the 2006 policy restricting use of trans fatty acids (TFAs) in New York City restaurants on change in serum TFA concentrations in New York City adults., Methods: Two cross-sectional population-based New York City Health and Nutrition Examination Surveys conducted in 2004 (n = 212) and 2013-2014 (n = 247) provided estimates of serum TFA exposure and average frequency of weekly restaurant meals. We estimated the geometric mean of the sum of serum TFAs by year and restaurant meal frequency by using linear regression., Results: Among those who ate less than 1 restaurant meal per week, geometric mean of the sum of serum TFAs declined 51.1% (95% confidence interval [CI] = 42.7, 58.3)-from 44.6 (95% CI = 39.7, 50.1) to 21.8 (95% CI = 19.3, 24.5) micromoles per liter. The decline in the geometric mean was greater (P for interaction = .04) among those who ate 4 or more restaurant meals per week: 61.6% (95% CI = 55.8, 66.7) or from 54.6 (95% CI = 49.3, 60.5) to 21.0 (95% CI = 18.9, 23.3) micromoles per liter., Conclusions: New York City adult serum TFA concentrations declined between 2004 and 2014. The indication of greater decline in serum TFAs among those eating restaurant meals more frequently suggests that the municipal restriction on TFA use was effective in reducing TFA exposure. Public Health Implications. Local policies focused on restaurants can promote nutritional improvements.

Reliable creatinine measurements are important to evaluate kidney function and for creatinine correction to reduce biological variability of other urinary analytes. A high-throughput, accurate liquid chromatography tandem mass spectrometry method for quantitation of human urinary creatinine has been developed and validated. Sample preparation was fully automated including cryovial decapping, sample ID scanning and two serial dilution steps. Quantitation was performed using a stable isotope-labeled internal standard. Multiplexed chromatographic separation of creatinine was achieved within a one-minute analysis and followed by tandem mass spectrometry in positive electrospray ionization mode. The precursor and product ions of creatinine and D 3 -creatinine were monitored in selected reaction monitoring mode. Method validation results showed reproducibility with within-run precision of 3.59, 3.49 and 2.84% and between-run precision of 4.01, 3.28 and 3.57% for low, medium and high quality control materials prepared from pooled donor urine, respectively. The method showed excellent accuracy with a bias of -1.94%, -0.78% and -1.07% for three levels of certified reference material. The calibration curve was linear throughout a 7.50-300 mg/dL (0.663-26.5 mmol/L) measurement range (R 2 = 0.999), with the mean slope of 0.0115 (95%CI, 0.0108-0.0122) and intercept of 0.0027 (95%CI, 0.0003-0.0051). The limit of detection (LOD) of the method was 3.17 mg/dL (0.280 mmol/L). Analytical specificity was achieved by chromatographically separating creatinine from potentially interfering creatine within a one-minute run and monitoring the Quantitation Ion/Confirmation Ion (QI/CI) ratios in samples. A simple, accurate, high-throughput method was successfully developed for measuring creatinine in human urine samples., Competing Interests: Conflict of Interest None of the authors has any conflicts of interest to disclose.

Background: Despite the usefulness of standard lipid parameters for cardiovascular disease risk assessment, undiagnosed residual risk remains high. Advanced lipoprotein testing (ALT) was developed to provide physicians with more predictive diagnostic tools. ALT methods separate and/or measure lipoproteins according to different parameters such as size, density, charge, or content, and equivalence of results across methods has not been demonstrated., Methods: Through a split-sample study, 25 clinical specimens (CSs) were assayed in 10 laboratories before and after freezing using the major ALT methods for non-HDL particles (non-HDL-P) or apolipoprotein B-100 (apoB-100) measurements with the intent to assess their comparability in the current state of the art., Results: The overall relative standard deviation (CV) of non-HDL-P and apoB-100 concentrations measured by electrospray differential mobility analysis, nuclear magnetic resonance, immunonephelometry, LC-MS/MS, and vertical autoprofile in the 25 frozen CSs was 14.1%. Within-method comparability was heterogeneous, and CV among 4 different LC-MS/MS methods was 11.4% for apoB-100. No significant effect of freezing and thawing was observed., Conclusions: This study demonstrates that ALT methods do not yet provide equivalent results for the measurement of non-HDL-P and apoB-100. The better agreement between methods harmonized to the WHO/IFCC reference material suggests that standardizing ALT methods by use of a common commutable calibrator will improve cross-platform comparability. This study provides further evidence that LC-MS/MS is the most suitable candidate reference measurement procedure to standardize apoB-100 measurement, as it would provide results with SI traceability. The absence of freezing and thawing effect suggests that frozen serum pools could be used as secondary reference materials., (© 2018 American Association for Clinical Chemistry.)

Ethylene oxide (EO), acrylamide (AA) and glycidamide (GA) exposures are associated with mammary tumors in animals. Currently available information about human exposure to these chemicals is limited creating the need for analytical methods to assess their exposure. We developed a sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to simultaneously quantitate hemoglobin (Hb) N-terminal valine adducts of AA (HbAA), GA (HbGA), and EO (HbEO) using modified Edman reaction. The limits of detection of this method were 3.9, 4.9 and 12.9 in pmol/g Hb for HbAA, HbGA and HbEO, respectively. The among-day and within-day precision for all analytes determined with three levels of quality control pools ranged from 2.2-13.0% in percent coefficient of variation (%CV). The accuracy determined by standard addition was between 94 and 111% among all analytes. The median HbAA, HbGA and HbEO values in 34 self-reported non-smokers were 64.9, 45.3 and 113.6 pmol/g Hb and in 70 self-reported smokers were 127.8, 69.6 and 237.1 pmol/g Hb, respectively. HbAA, HbGA, and HbEO were detectable in all samples suggesting that the described method is suitable for measuring hemoglobin adducts of AA, GA and EO in the general population. This high throughput method can process 148 samples in 8 h. The HbEO/HbGA ratio appears independent of the HbAA levels in non-smokers and decreases with increasing HbAA concentration in smokers. This new method is suitable for measuring human exposure to AA, GA and EO and can provide further insight into the metabolism of these chemicals in humans., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Purpose: Chemicals with hormonelike activity, such as estrogenic isoflavones, may perturb human development. Infants exclusively fed soy-based formula are highly exposed to isoflavones, but their physiologic responses remain uncharacterized. Estrogen-responsive postnatal development was compared in infants exclusively fed soy formula, cow-milk formula, and breast milk., Methods: We enrolled 410 infants born in Philadelphia-area hospitals between 2010 and 2014; 283 were exclusively fed soy formula (n = 102), cow-milk formula (n = 111), or breast milk (n = 70) throughout the study (birth to 28 or 36 weeks for boys and girls, respectively). We repeatedly measured maturation index (MI) in vaginal and urethral epithelial cells using standard cytological methods, uterine volume and breast-bud diameter using ultrasound, and serum estradiol and follicle-stimulating hormone levels. We estimated MI, organ-growth, and hormone trajectories by diet using mixed-effects regression splines., Results: Maternal demographics did not differ between cow-milk-fed and soy-fed infants but did differ between formula-fed and breastfed infants. Vaginal-cell MI trended higher (P = 0.01) and uterine volume decreased more slowly (P = 0.01) in soy-fed girls compared with cow-milk-fed girls; however, their trajectories of breast-bud diameter and hormone concentrations did not differ. We observed no significant differences between boys fed cow-milk vs soy formula; estradiol was not detectable. Breastfed infants differed from soy-formula-fed infants in vaginal-cell MI, uterine volume, and girls' estradiol and boys' breast-bud diameter trajectories., Conclusions: Relative to girls fed cow-milk formula, those fed soy formula demonstrated tissue- and organ-level developmental trajectories consistent with response to exogenous estrogen exposure. Studies are needed to further evaluate the effects of soy on child development.

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator based on its ability to fulfill its intended use in a calibration traceability scheme to produce equivalent clinical sample (CS) results among different measurement procedures (MPs) for the same measurand. Three sources of systematic error are elucidated in the context of creating the calibration model for translating MP signals to measurand amounts: calibration fit, calibrator level trueness, and commutability. An example set of 40 CS results from 7 MPs is used to illustrate estimation of bias and variability for each MP. The candidate RM is then used to recalibrate each MP, and its effectiveness in reducing the systematic error among the MPs within an acceptable level of equivalence based on medical requirements confirms its commutability for those MPs. The RM is declared noncommutable for MPs for which, after recalibration, the CS results do not agree with those from other MPs. When a lack of agreement is found, other potential causes, including lack of calibration fit, should be investigated before concluding the RM is noncommutable. The RM is considered fit for purpose for those MPs where commutability is demonstrated., (© 2017 American Association for Clinical Chemistry.)

A process is described to assess the commutability of a reference material (RM) intended for use as a calibrator, trueness control, or external quality assessment sample based on the difference in bias between an RM and clinical samples (CSs) measured using 2 different measurement procedures (MPs). This difference in bias is compared with a criterion based on a medically relevant difference between an RM and CS results to make a conclusion regarding commutability. When more than 2 MPs are included, the commutability is assessed pairwise for all combinations of 2 MPs. This approach allows the same criterion to be used for all combinations of MPs included in the assessment. The assessment is based on an error model that allows estimation of various random and systematic sources of error, including those from sample-specific effects of interfering substances. An advantage of this approach is that the difference in bias between an RM and the average bias of CSs at the concentration (i.e., amount of substance present or quantity value) of the RM is determined and its uncertainty estimated. An RM is considered fit for purpose for those MPs for which commutability is demonstrated., (© 2017 American Association for Clinical Chemistry.)

Commutability is a property of a reference material (RM) that relates to the closeness of agreement between results for an RM and results for clinical samples (CSs) when measured by ≥2 measurement procedures (MPs). Commutability of RMs used in a calibration traceability scheme is an essential property for them to be fit for purpose. Similarly, commutability of trueness controls or external quality assessment samples is essential when those materials are used to assess trueness of results for CSs. This report is part 1 of a 3-part series describing how to assess commutability of RMs. Part 1 defines commutability and addresses critical components of the experimental design for commutability assessment, including selection of individual CSs, use of pooled CSs, qualification of MPs for inclusion, establishing criteria for the determination that an RM is commutable, generalization of commutability conclusions to future measurements made with the MPs included in the assessment, and information regarding commutability to be included in the certificate for an RM. Parts 2 and 3 in the series present 2 different statistical approaches to commutability assessment that use fixed criteria related to the medical decisions that will be made using the laboratory test results., (© 2017 American Association for Clinical Chemistry.)

Trans-fatty acids (TFA) are geometric isomers of naturally occurring cis-fatty acids. High dietary TFA intake has been associated with risk factors for cardiovascular disease. However, little is known about TFA levels in humans. To address this data need, we developed and validated a new isotope dilution-gas chromatography-negative chemical ionization-mass spectrometry (ID-GC-NCI-MS) method for quantitation of 27 fatty acids (FA) including 4 major TFA in human plasma, serum, and red blood cells (RBC) from 66 donors. Quantitation was performed with 18 isotope labeled internal standards and results are presented in μM and % of total FA. This method has high sensitivity and specificity due to use of pentafluorobenzyl-bromide derivatization combined with NCI-MS and a 200m column to optimize positional and geometric FA isomer separation. The four major TFA, palmitelaidic acid, elaidic acid, trans-vaccenic acid, and linoelaidic acid, were detected in all samples, with median total TFA concentrations of 17.7μM in plasma, 19.6μM in serum, and 21.5μM in RBC. The % of total FA for the TFA was 0.20% in plasma, 0.20% in serum, and 0.30% in RBC. Patterns for % FA are similar to those reported in other studies. We developed a highly specific, ID-GC-NCI-MS method to quantitate TFA and other FA in humans., (Published by Elsevier B.V.)

Reliable measurement of total testosterone and estradiol is critical for their use as biomarkers of hormone-related disorders in patient care and translational research. We developed and validated a mass spectrometry method to simultaneously quantify these analytes in human serum without chemical derivatization. Serum is equilibrated with isotopic internal standards and treated with acidic buffer to release hormones from their binding proteins. Lipids are isolated and polar impurities are removed by two serial liquid-liquid extraction steps. Total testosterone and estradiol are measured using liquid chromatography tandem mass spectrometry (LC-MS/MS) in combination of positive and negative electrospray ionization modes. The method shows broad analytical measurement range for both testosterone 0.03-48.5 nM (0.75-1400 ng/dL) and estradiol 11.0-5138 pM (2.99-1400 pg/mL) and excellent agreement with certified reference materials (mean bias less than 2.1% to SRM 971, BCR 576, 577, and 578) and a high order reference method (mean bias 1.25% for testosterone and -0.84% for estradiol). The high accuracy of the method was monitored and certified by CDC Hormone Standardization (HoSt) Program for 2 years with mean bias -0.7% (95% CI -1.6% to 0.2%) for testosterone and 0.1% (95% CI -2.2% to 2.3%) for estradiol. The method precision over a 2-year period for quality control pools at low, medium, and high concentrations was 2.7-2.9% for testosterone and 3.3-5.3% for estradiol. With the consistently excellent accuracy and precision, this method is readily applicable for high-throughput clinical and epidemiological studies.

Formaldehyde (FA) is an environmental chemical classified as a human carcinogen. It is highly reactive and can bind covalently with hemoglobin (Hb) to produce Hb adducts. Measurement of these Hb adducts provides valuable information about exposure to this chemical. We developed a robust, ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for quantifying FA-Hb adducts in red blood cells. The method measures the FA-VHLTPEEK peptide after trypic digestion. The peptide is a FA adduct at the N-terminus of the beta chain of human Hb. Method mean (±SD) accuracy, determined by recovery in quality control and blank material was 103.2% ± 8.11. The mean among-day and within-day coefficients of variation determined at three concentration levels (%CV) were 9.2% (range: 7.2-10.2%) and 4.9% (range 3.1-7.3%), respectively. The limit of detection was 3.4 nmol/g Hb. This method was applied to the analysis of 135 human blood samples, and FA-VHLTPEEK was detected in all study samples. FA-VHLTPEEK concentrations were not significantly different between smokers and nonsmokers. This work is the first validated UPLC-MS/MS method in which a FA peptide derived from a FA-Hb adduct could be used to monitor exposure to FA in population studies.

Background: The consumption of trans fatty acids (TFAs) is associated with an increased risk of cardiovascular disease, and reducing their consumption is a major public health objective. Food intake studies have provided estimates for TFA concentrations in the US population; however, there is a need for data on TFA blood concentrations in the population. Objective: The objective of this study was to determine plasma TFA concentrations in a nationally representative group of fasted adults in the US population in NHANES samples from 1999-2000 and 2009-2010. Design: Four major TFAs [palmitelaidic acid (C16:1n-7t), trans vaccenic acid (C18:1n-7t), elaidic acid (C18:1n-9t), and linoelaidic acid (C18:2n-6t,9t)] were measured in plasma in 1613 subjects from NHANES 1999-2000 and 2462 subjects from NHANES 2009-2010 by gas chromatography-mass spectrometry. Geometric means and distribution percentiles were calculated for each TFA and their sum by age, sex, and race/ethnicity (non-Hispanic white, non-Hispanic black, Mexican American), and covariate-adjusted geometric means were computed by using a model that included these demographic and other dietary factors, as well as survey year and any significant interaction terms. Results: These nationally representative data for the adult US population show that TFA concentrations were 54% lower in NHANES 2009-2010 than in NHANES 1999-2000. Covariate-adjusted geometric means for the sum of the 4 TFAs were 81.4 μmol/L (95% CI: 77.3, 85.6 μmol/L) and 37.8 μmol/L (95% CI: 36.4, 39.4 μmol/L) in NHANES 1999-2000 and 2009-2010, respectively. Even with the large decline in TFA concentrations, differences between demographic subgroups were comparable in the 2 surveys. Conclusion: The results indicate an overall reduction in TFA concentrations in the US population and provide a valuable baseline to evaluate the impact of the recent regulation categorizing TFAs as food additives., (© 2017 American Society for Nutrition.)

Background: Reference ranges for testosterone are essential for making a diagnosis of hypogonadism in men., Objective: To establish harmonized reference ranges for total testosterone in men that can be applied across laboratories by cross-calibrating assays to a reference method and standard., Population: The 9054 community-dwelling men in cohort studies in the United States and Europe: Framingham Heart Study; European Male Aging Study; Osteoporotic Fractures in Men Study; and Male Sibling Study of Osteoporosis., Methods: Testosterone concentrations in 100 participants in each of the four cohorts were measured using a reference method at Centers for Disease Control and Prevention (CDC). Generalized additive models and Bland-Altman analyses supported the use of normalizing equations for transformation between cohort-specific and CDC values. Normalizing equations, generated using Passing-Bablok regression, were used to generate harmonized values, which were used to derive standardized, age-specific reference ranges., Results: Harmonization procedure reduced intercohort variation between testosterone measurements in men of similar ages. In healthy nonobese men, 19 to 39 years, harmonized 2.5th, 5th, 50th, 95th, and 97.5th percentile values were 264, 303, 531, 852, and 916 ng/dL, respectively. Age-specific harmonized testosterone concentrations in nonobese men were similar across cohorts and greater than in all men., Conclusion: Harmonized normal range in a healthy nonobese population of European and American men, 19 to 39 years, is 264 to 916 ng/dL. A substantial proportion of intercohort variation in testosterone levels is due to assay differences. These data demonstrate the feasibility of generating harmonized reference ranges for testosterone that can be applied to assays, which have been calibrated to a reference method and calibrator., (Copyright © 2017 by the Endocrine Society)

Parathyroid hormone (PTH) measurement in serum or plasma is a necessary tool for the exploration of calcium/phosphate disorders, and is widely used as a surrogate marker to assess skeletal and mineral disorders associated with chronic kidney disease (CKD), referred to as CKD-bone mineral disorders (CKD-MBD). CKD currently affects >10% of the adult population in the United States and represents a major health issue worldwide. Disturbances in mineral metabolism and fractures in CKD patients are associated with increased morbidity and mortality. Appropriate identification and management of CKD-MBD is therefore critical to improving clinical outcome. Recent increases in understanding of the complex pathophysiology of CKD, which involves calcium, phosphate and magnesium balance, and is also influenced by vitamin D status and fibroblast growth factor (FGF)-23 production, should facilitate such improvement. Development of evidence-based recommendations about how best to use PTH is limited by considerable method-related variation in results, of up to 5-fold, as well as by lack of clarity about which PTH metabolites these methods recognise. This makes it difficult to compare PTH results from different studies and to develop common reference intervals and/or decision levels for treatment. The implications of these method-related differences for current clinical practice are reviewed here. Work being undertaken by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) to improve the comparability of PTH measurements worldwide is also described., (Copyright © 2016. Published by Elsevier B.V.)