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ImportanceSex-specific differences in the commonly used cardiac biomarkers high-sensitivity cardiac troponin (hs-cTn) and N-terminal pro–brain natriuretic peptide (NT-proBNP) are apparent. There is an absence of medical literature delineating the concentration differences for these biomarkers in transgender individuals without cardiac disease.ObjectiveTo determine the distribution of hs-cTn and NT-proBNP in healthy transgender people.Design, Setting, and ParticipantsIn this cross-sectional prospective study, healthy transgender individuals prescribed testosterone or estradiol for 12 months or more were recruited from internal medicine and primary care clinics that specialize in transgender medical care between November 1, 2017, and July 1, 2018.ExposuresTestosterone or estradiol for 12 months.Main Outcomes and MeasuresConcentrations for hs-cTnI (troponin I), hs-cTnT (troponin T), and NT-proBNP were measured.ResultsTransgender people prescribed testosterone (n = 79; mean [SD] age, 28.8 [7.8] years) or estrogen (n = 93; mean [SD] age, 35.1 [11.7] years) were recruited. The concentration of hs-cTn was significantly higher in transgender men relative to transgender women. For Abbott hs-cTnI levels, the median (IQR) concentration observed in transgender men and women was 0.9 (0.6-1.7) ng/L and 0.6 (0.3-1.0) ng/L, respectively. Results were similar across 2 additional hs-cTn assays. In contrast, NT-proBNP level was higher in transgender women. The median (IQR) NT-proBNP concentration was significantly higher in transgender women ( 49 [32-86] ng/L) than in transgender men (17 [13-27] ng/L).Conclusions and RelevanceFindings of this cross-sectional study suggest that the differences in concentration for hs-cTn and NT-proBNP between transgender men and women were similar to what is observed between cisgender men and women. Sex hormones, rather than sex assigned at birth, may be a stronger driver of the observed concentration differences between healthy men and women for biomarkers of cardiac disease.

The International Federation of Clinical Chemistry Committee on Clinical Application of Cardiac Bio-Markers provides evidence-based educational documents to facilitate uniform interpretation and utilization of cardiac biomarkers in clinical laboratories and practice. The committee’s goals are to improve the understanding of certain key analytical and clinical aspects of cardiac biomarkers and how these may interplay in clinical practice. Measurement of high-sensitivity cardiac troponin (hs-cTn) assays is a cornerstone in the clinical evaluation of patients with symptoms and/or signs of acute cardiac ischemia. To define myocardial infarction, the Universal Definition of Myocardial Infarction requires patients who manifest with features suggestive of acute myocardial ischemia to have at least one cTn concentration above the sex-specific 99th percentile upper reference limit (URL) for hs-cTn assays and a dynamic pattern of cTn concentrations to fulfill the diagnostic criteria for MI. This special report provides an overview of how hs-cTn 99th percentile URLs should be established, including recommendations about prescreening and the number of individuals required in the reference cohort, how statistical analysis should be conducted, optimal preanalytical and analytical protocols, and analytical/biological interferences or confounds that can affect accurate determination of the 99th percentile URLs. This document also provides guidance and solutions to many of the issues posed.

The International Federation of Clinical Chemistry Committee on Clinical Applications of Cardiac Biomarkers (IFCC C-CB) provides educational documents to facilitate the interpretation and use of cardiac biomarkers in clinical laboratories and practice. Our aim is to improve the understanding of certain key analytical and clinical aspects of cardiac biomarkers and how these may interplay. Measurements of cardiac troponin (cTn) have a prominent place in the clinical work-up of patients with suspected acute coronary syndrome. It is therefore important that clinical laboratories know how to recognize and assess analytical issues. Two emerging analytical issues resulting in falsely high cTn concentrations, often several fold higher than the upper reference limit (URL), are antibody-mediated assay interference due to long-lived cTn-antibody complexes, called macrotroponin, and crosslinking antibodies that are frequently referred to as heterophilic antibodies. We provide an overview of antibody-mediated cTn assay interference and provide recommendations on how to confirm the interference and interpret the results.

Suppression of tumorigenicity 2 (ST2) has important cardiovascular prognostic value in community patients; however, previous analyses have utilized non-sex specific cut-off values. We assessed whether sex-specific ST2 cut-off values would improve the prognostic utility of ST2 in the asymptomatic community.A total of 2042 participants underwent clinical assessment and echocardiographic evaluation. Baseline measurements of high sensitivity troponin, natriuretic peptides and ST2 were obtained in 1681 individuals. ST2, cardiac biomarkers and associated co-morbidities were evaluated by sex-specific ST2 quartile analysis. ST2 concentrations were also analysed as dichotomous variables defined as being above the sex-specific cut-off for each the outcomes of heart failure (HF), major adverse cardiac event (MACE) and mortality.Median ST2 concentration was 29.4 ng/mL in male subjects and 24.1 ng/mL in female subjects. Higher ST2 concentrations were associated with incident HF (These data suggest that sex-specific cut-offs, greater than non-sex specific cut-offs, significantly impact the prognostic value of the biomarker ST2 in the asymptomatic community cohort.Clinical SignificanceSuppression of tumorigenicity 2 (ST2) is a biomarker which has known associations with heart failure (HF), major adverse cardiac events (MACEs) and mortality in the general population.Recent data support the concept of sex-specific cut off values and individualized approaches based on sex to predict cardiovascular disease. Given the difference in pathobiology between the sexes, the fact that such approaches improve risk stratification is understandable. Thus, when sex-specific treatments are developed, this may similarly lead to improved outcomes.The use of sex-specific ST2 cut-off values significantly improved the prognostic value in predicting HF, MACE, and mortality in an asymptomatic community. This prognostication was particularly strong for HF with preserved ejection fraction and remained clinically significant following adjustment for cardiac co-morbidities and other traditional cardiac biomarkers (NTproBNP and hscTnI).

Background Concerns exist regarding how the 99th percentile upper reference limit (URL) of cardiac troponin (cTn) is determined and whether it should be derived from normal healthy individuals. Content The 99th percentile URL of cTn is an important criterion to standardize the diagnosis of myocardial infarction (MI) for clinical, research, and regulatory purposes. Statistical heterogeneity in its calculation exists but recommendations have been proposed. Some negativity has resulted from the fact that with some high-sensitivity (hs) cTn assays, a greater number of increases above the 99th percentile are observed when transitioning from a contemporary assay. Increases reflect acute or chronic myocardial injury and provide valuable diagnostic and prognostic information. The etiology of increases can sometimes be difficult to determine, making a specific treatment approach challenging. For those reasons, some advocate higher cutoff concentrations. This approach can contribute to missed diagnoses. Contrary to claims, neither clinical or laboratory guidelines have shifted away from the 99th percentile. To support the diagnosis of acute MI, the 99th percentile URL remains the best-established approach given the absence of cTn assay standardization. Importantly, risk stratification algorithms using hs-cTn assays predict the possibility of MI diagnoses established using the 99th percentile. Summary The 99th percentile of cTn remains the best-established criterion for the diagnosis of acute MI. While not perfect, it is analytically and clinically evidence-based. Until there are robust data to suggest some other approach, staying with the 99th percentile, a threshold that has served the field well for the past 20 years, appears prudent.

Background Measurement of cholesterol within lipoprotein subfractions may aid in cardiovascular disease prediction. Simple, homogenous enzymatic assays for the direct measurement of lipoprotein subfractions have been developed to measure small dense low-density lipoprotein cholesterol (sdLDL-C), high-density lipoprotein-3 cholesterol (HDL3-C), and triglyceride-rich lipoprotein (TRL-C) cholesterol. The objective of this study was to determine biological variability for sdLDL-C, HDL3-C, and TRL-C in a healthy reference population to facilitate interpretation of these analytes. Methods Serum samples were collected from 24 healthy subjects (n = 14 female/10 male) daily for 3 days while non-fasting, and daily for 5 days, weekly for 4 weeks, and monthly for 6 months after overnight fasting. sdLDL-C, HDL3-C, and TRL-C cholesterol were measured by homogenous enzymatic assays. Sources of variability (between-subject, within-subject, and analytical) were calculated using random-effects regression models. Reference change value (RCV) and index of individuality (II) for each time period were determined from the variance components. Results Analytic variability (daily, weekly, and monthly CVA) was Conclusions sdLDL-C, HDL3-C, and TRL-C showed moderate within-subject variability, but high between-subject variability, in a healthy reference population. Given the high individuality of each analyte, population-based reference intervals may be inadequate to detect clinically significant changes.

Background and objectives Glomerular hyperfiltration has been considered to be a contributing factor to the development of diabetic kidney disease (DKD). To address this issue, we analyzed GFR follow-up data on participants with type 1 diabetes undergoing 125 I-iothalamate clearance on entry into the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications study. Design, setting, participants, & measurements This was a cohort study of DCCT participants with type 1 diabetes who underwent an 125 I-iothalamate clearance (iGFR) at DCCT baseline. Presence of hyperfiltration was defined as iGFR levels ≥140 ml/min per 1.73 m 2 , with secondary thresholds of 130 or 150 ml/min per 1.73 m 2 . Cox proportional hazards models assessed the association between the baseline hyperfiltration status and the subsequent risk of reaching an eGFR 2 . Results Of the 446 participants, 106 (24%) had hyperfiltration (iGFR levels ≥140 ml/min per 1.73 m 2 ) at baseline. Over a median follow-up of 28 (interquartile range, 23, 33) years, 53 developed an eGFR 2 . The cumulative incidence of eGFR 2 at 28 years of follow-up was 11.0% among participants with hyperfiltration at baseline, compared with 12.8% among participants with baseline GFR 2 . Hyperfiltration was not significantly associated with subsequent risk of developing an eGFR 2 in an unadjusted Cox proportional hazards model (hazard ratio, 0.83; 95% confidence interval, 0.43 to 1.62) nor in an adjusted model (hazard ratio, 0.77; 95% confidence interval, 0.38 to 1.54). Application of alternate thresholds to define hyperfiltration (130 or 150 ml/min per 1.73 m 2 ) showed similar findings. Conclusions Early hyperfiltration in patients with type 1 diabetes was not associated with a higher long-term risk of decreased GFR. Although glomerular hypertension may be a mechanism of kidney injury in DKD, higher total GFR does not appear to be a risk factor for advanced DKD.

OBJECTIVE High-sensitivity cardiac troponin-T (hs-cTnT) and N-terminal prohormone of B-type natriuretic peptide (NT-proBNP), biomarkers of cardiovascular disease (CVD) and heart failure, respectively, have not been widely studied in type 1 diabetes (T1D). We evaluated whether their assessment in T1D enhances the prediction of CVD and major adverse cardiovascular events (MACE). RESEARCH DESIGN AND METHODS hs-cTnT and NT-proBNP were analyzed on the Roche Cobas E601 using the first available stored specimen (n = 581; mean age 29 years and diabetes duration 21 years). CVD was defined as CVD death, myocardial infarction, coronary revascularization, angina, ischemia, or stroke, and MACE as CVD death, myocardial infarction, or stroke. RESULTS Median hs-cTnT (5.0 ng/L; interquartile range CONCLUSIONS Sex differences were observed in the concentration and predictive ability of hs-cTnT and NT-proBNP in T1D. Overall, their addition to traditional risk factor models increased the area under the curve for neither CVD nor MACE.

Objective: High-sensitivity cardiac Troponin-T (hs-cTnT) and N-terminal pro B-Type natriuretic peptide (NT-proBNP), biomarkers of cardiovascular disease (CVD) and heart failure, respectively, have not been widely studied in type 1 diabetes (T1D). We evaluated whether their assessment in T1D enhances the prediction of CVD and major atherosclerotic cardiovascular events (MACE). Research Design and Methods: hs-cTnT and NT-proBNP were analyzed on the Roche Cobas E601 utilizing the first available stored specimen (n=581; mean age 29 and duration 21 years). CVD was defined as CVD death, myocardial infarction, coronary revascularization, angina, ischemia, or stroke and MACE as CVD death, myocardial infarction, or stroke. Results: Median hs-cTnT (5.0 ng/L, IQR: Conclusions: Sex differences were observed in the concentration and predictive ability of hs-cTnT and NT-proBNP in T1D. Overall, their addition to traditional risk factor models increased the area under the curve for neither CVD nor MACE.

Background Many CpGs become hyper or hypo-methylated with age. Multiple methods have been developed by Horvath et al. to estimate DNA methylation (DNAm) age including Pan-tissue, Skin & Blood, PhenoAge, and GrimAge. Pan-tissue and Skin & Blood try to estimate chronological age in the normal population whereas PhenoAge and GrimAge use surrogate markers associated with mortality to estimate biological age and its departure from chronological age. Here, we applied Horvath’s four methods to calculate and compare DNAm age in 499 subjects with type 1 diabetes (T1D) from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study using DNAm data measured by Illumina EPIC array in the whole blood. Association of the four DNAm ages with development of diabetic complications including cardiovascular diseases (CVD), nephropathy, retinopathy, and neuropathy, and their risk factors were investigated. Results Pan-tissue and GrimAge were higher whereas Skin & Blood and PhenoAge were lower than chronological age (p < 0.0001). DNAm age was not associated with the risk of CVD or retinopathy over 18–20 years after DNAm measurement. However, higher PhenoAge (β = 0.023, p = 0.007) and GrimAge (β = 0.029, p = 0.002) were associated with higher albumin excretion rate (AER), an indicator of diabetic renal disease, measured over time. GrimAge was also associated with development of both diabetic peripheral neuropathy (OR = 1.07, p = 9.24E−3) and cardiovascular autonomic neuropathy (OR = 1.06, p = 0.011). Both HbA1c (β = 0.38, p = 0.026) and T1D duration (β = 0.01, p = 0.043) were associated with higher PhenoAge. Employment (β = − 1.99, p = 0.045) and leisure time (β = − 0.81, p = 0.022) physical activity were associated with lower Pan-tissue and Skin & Blood, respectively. BMI (β = 0.09, p = 0.048) and current smoking (β = 7.13, p = 9.03E−50) were positively associated with Skin & Blood and GrimAge, respectively. Blood pressure, lipid levels, pulse rate, and alcohol consumption were not associated with DNAm age regardless of the method used. Conclusions Various methods of measuring DNAm age are sub-optimal in detecting people at higher risk of developing diabetic complications although some work better than the others.

Ionized Mg (iMg) is considered the biologically active fraction of circulating total Mg (tMg). It is possible that iMg may be a more physiologically relevant marker than tMg. Using data from a double-blind pilot randomized controlled trial, we tested (1) whether oral Mg supplementation will increase iMg concentrations compared with placebo and (2) the relationship between iMg and tMg at baseline. Additionally, we evaluated the agreement between iMg measured in fresh whole blood versus stored samples. A total of fifty-nine participants were randomized 1:1 to oral Mg supplementation (400 mg/day, Mg Oxide) or placebo for 10 weeks. Fasting blood samples were obtained at baseline and follow-up. The analysis used linear regression and an intent-to-treat approach. Participants were generally healthy, the mean age was 62, and 73% were female. The baseline iMg and tMg were modestly and positively associated (r = 0.50). The ratio of baseline iMg to tMg was 64%. The mean supplement effect on iMg was 0.03 mmol/L (95% CI:0.01, 0.05) for Mg supplementation versus placebo. The supplement effect on iMg was not statistically significantly different according to baseline iMg status (above/below median). Compared to fresh blood, iMg was consistently higher in refrigerated and frozen samples by 0.14 and 0.20 mmol/L, respectively. In this relatively healthy adult population, Mg supplementation over 10 weeks resulted in increased iMg concentrations. Whether iMg is a more appropriate measure of Mg status than tMg, and the public health or clinical utility of measuring iMg remains to be determined.

Tweets. Hashtags. Blogs. Hangouts. Podcasts. Wikis. What do these social media platforms and verbiage have to do with education, and why should you care? Social media is used on a daily and even hourly basis as a modality to rapidly and effectively communicate, educate, and learn. Some medical specialties have quickly adopted and embraced social media, particularly in the fields of emergency medicine, family medicine, and pediatrics. Other fields, including laboratory medicine and pathology, have had a much slower uptake that may directly correlate with the amount of patient–physician interaction. The specialties that have a high rate of use have also catalyzed implementation of social media into medical education and residency program curriculum, and used it as a modality to recruit physicians and staff at all levels. In addition, the free open-access movement (FOAM)9 has altered how medical education resources and content are accessed by physicians and patients, ultimately shifting and removing geographical and income barriers across the globe. Laboratorians and pathologists have a unique opportunity to move outside the 4 walls of the laboratory and engage other physicians, residents, and even patients in a way that has never been done before. Perhaps it is time we communicate beyond the results reported in the electronic medical record, and instead discuss the value and contributions that our laboratories provide every day. Here, 6 experts in the social media field share their thoughts on social media use, challenges, and opportunities. What are the primary forms of social media you use from a professional and educational standpoint, and how long have you been using them? How has your profession and/or colleagues responded (i.e., fast or slow adopters) to using social media? What do you believe are the primary contributing factors to this response? Shannon Haymond: My primary format for this purpose is …

The guideline-recommended lipid panel for cardiovascular disease (CVD) risk assessment measures total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, and calculated low-density lipoprotein (LDL) cholesterol. Measured cholesterol in subfractions of HDL and LDL purportedly improve CVD risk prediction. Homogenous enzymatic methods are now available for measurement of the cholesterol within small dense LDL (sLDL), small dense HDL (HDL3), and triglyceride-rich lipoproteins (TRL). For meaningful interpretation of these measurements, an understanding of the potential sources and extent of result variability is needed. The smallest difference between serial measurements within a patient that likely reflects a change in clinical status is called the reference change value (RCV). Biological variability and reference change values (RCV) are well-characterized for basic lipids but there is limited information for sLDL, HDL3 or TRL. The objective of this study was to determine intra- and inter-individual variability for sLDL, HDL3, and TRL in a healthy reference population. Serum samples were collected from 24 healthy subjects (n=14 female/10 male) daily for three days (non-fasting), daily for five days (fasting), weekly for four weeks (fasting), and monthly for 7 months (fasting). sLDL, HDL3, and TRL cholesterol were measured in duplicate by enzymatic colorimetric assays (Denka, Japan) on a Roche Cobas c501. Each source of variability (between subject, within subject, and analytical) was calculated using random-effects regression models to estimate each variance component including the overall variation, standard deviation (SD), coefficient of variation (CV), and proportion of total variance (between-subject, within-subject, and analytical). Using these analytical and biological variances, the reference change value (RCV), index of individuality (IoI), and intraclass correlation coefficient (ICC) were determined. Analytic variability (CVa) from monthly testing was 1.2%, 1.1%, and 1.5% for sLDL, HDL3, and TRL, respectively. Monthly within-subject variability (CVw) was 17.1% for sLDL, 7.4% for HDL3 and 25.7% for TRL. Monthly between-subject variability (CVb) was 32.2%, 13.93%, and 33.4% for sLDL, HDL3, and TRL, respectively. Most of the monthly variation was attributed to between-subject variation for all three tests. Within-subject variation accounted for 37% of TRL variation and 22% for both sLDL and HLD3. Within-subject RCVs for monthly measurements were 16.9mg/dL for sLDL, 5.3mg/dL for HDL3, and 15.1mg/dL for TRL. IoIs for monthly testing were 0.81 for TRL, 0.57 for sLDL, and 0.61 for HDL3. Our data demonstrate that sLDL, HDL3, and TRL show low analytical variability, moderate within-subject variability, but high between-subject variability when measured by homogenous assays in a healthy population. The IoI value (>0.6) for TRL suggests use of a reference interval is appropriate for result interpretation. Conversely, clinical cut-points may be more useful than reference intervals for sLDL and HDL3 which had IoIs ~0.6. These findings may be useful for clinical interpretation, particularly when comparing successive measurements of these analytes.

Our purpose was to determine a) overall and sex-specific 99th percentile upper reference limits (URL) and b) influences of statistical methods and comorbidities on the URLs.Heparin plasma from 838 normal subjects (423 men, 415 women) were obtained from the AACC (Universal Sample Bank). The cobas e602 measured cTnT (Roche Gen 5 assay); limit of detection (LoD), 3ng/L. Hemoglobin A1c (URL 6.5%), NT-proBNP (URL 125ng/L) and eGFR (60mL/min/1.73m355 men and 339 women remained after exclusions. Overall50% of subjects had measureable concentrations ≥ LoD: 45.6% no exclusion, 43.5% after exclusion; compared to men: 68.1% no exclusion, 65.1% post exclusion; women: 22.7% no exclusion, 20.9% post exclusion. The statistical method used influenced URLs as follows: pre/post exclusion overall, NP 16/16ng/L, HDE 17/17ng/L, R not available; men NP 18/16ng/L, HDE 21/19ng/L, R 16/11ng/L; women NP 13/10ng/L, HDE 14/14ng/L, R not available.We demonstrated that a) the Gen 5 cTnT assay does not meet the IFCC guideline for high-sensitivity assays, b) surrogate biomarkers significantly lowers the URLs and c) statistical methods used impact URLs. Our data suggest lower sex-specific cTnT 99th percentiles than reported in the FDA approved package insert. We emphasize the importance of detailing the criteria used to include and exclude subjects for defining a healthy population and the statistical method used to calculate 99th percentiles and identify outliers.

A number of national and international guidelines recommend treatment to low-density lipoprotein cholesterol (LDL-C)70 mg/dL. Comparing the performance of the Friedewald and a novel LDL-C estimate at these concentrations in a nationally representative and clinical cohorts can inform best practices.The objectives of the study were to evaluate concordance between Friedewald-estimated LDL-C and novel-estimated LDL-C and compare with other atherogenic parameters when the estimated LDL-C is70 mg/dL.Atherogenic lipid parameters were assessed in a cross-sectional analysis among participants with a Friedewald-estimated LDL-C70 mg/dL from National Health and Nutrition Examination Survey (NHANES) 2011-2012 (n = 334), Johns Hopkins (n = 896), and Mayo Clinic (n = 1151). Novel LDL-C was estimated using an individualized factor to account for heterogeneity in the triglyceride to very low-density lipoprotein cholesterol ratio. Participants were classified as concordant if their LDL-C was70 mg/dL by both equations and discordant if ≥70 mg/dL by the novel equation.Among NHANES participants not on statin therapy, 10% had LDL-C70 mg/dL by both the Friedewald and novel equations. Overall, 15% of participants from NHANES, 20% from Johns Hopkins, and 20% from Mayo Clinic had discordant LDL-C values. In all 3 cohorts, nearly one-fourth of participants in the discordant group had an LDL-C estimate of ≥80 mg/dL (ie, ≥10 mg/dL higher) by the novel equation. Compared with the concordant group, the discordant group had significantly higher median concentrations of non-high-density lipoprotein cholesterol (HDL-C; 101-104 mg/dL vs 74-79 mg/dL) and apolipoprotein B (apoB; 65-72 mg/dL vs 47-57 mg/dL). In NHANES, wherein statins use was recorded, a similarly higher atherogenic burden by non-HDL-C and apoB levels was observed on and off statin therapy in the discordant group.In a nationally representative sample, a hospital laboratory, and a reference laboratory, approximately one-fifth of individuals with Friedewald-estimated LDL-C70 mg/dL have a value ≥70 mg/dL using the novel LDL-C equation. These individuals also have significantly higher non-HDL-C and apoB concentrations, conferring an increased risk for cardiovascular disease. Accordingly, ongoing use of Friedewald estimation may lead to the misclassification of high-risk individuals and subsequent under-utilization of lipid-lowering therapies. Further investigations are necessary to confirm these findings in patients using proprotein convertase subtilisin-kexin type 9 inhibitors.

BACKGROUNDB-type natriuretic peptides (BNPs) are used clinically to diagnose and monitor heart failure and are present in the circulation as multiple proBNP-derived fragments. We investigated the specificity of BNP immunoassays with glycosylated and nonglycosylated BNP, N-terminal proBNP (NT-proBNP), and proBNP peptides to probe the cross-reactivity of each assay.METHODSNine B-type natriuretic peptides were studied,including synthetic and recombinant BNP (Shionogi, Scios, Mayo), human and synthetic glycosylated and nonglycosylated NT-proBNP (HyTest, Roche Diagnostics), and human glycosylated and nonglycosylated proBNP (HyTest, Scios). Five BNP [Abbott, Abbott POC, Alere, Beckman Coulter, Siemens (Centaur)], 9 NT-proBNP [Ortho-Clinical Diagnostics, Roche, Response, bioMerieux, Siemens (Dimension, Immulite, Stratus CS), Mitsubishi] and 3 research-use-only proBNP immunoassays [Biosite (Alere), Bio-Rad, Goetze] were evaluated. Specificity was assessed by calculating the recovery between baseline and peptide-spiked human plasma pools at target concentrations of 100 ng/L BNP, 300 ng/L proBNP, or 450 ng/L NT-proBNP. All assays were performed in duplicate.RESULTSBNP and NT-proBNP assays demonstrated substantial cross-reactivity with proBNP peptides. NT-proBNP assays do not detect glycosylated forms of either NT-proBNP or proBNP. proBNP assays preferentially detect the BNP 1–32 peptide and have minimal cross-reactivity with BNP peptides and glycosylated proBNP.CONCLUSIONSBNP or NT-proBNP results are not transferable among the current existing immunoassays owing to their differences in cross-reactivity and ability to detect various glycosylated forms of proBNP-derived fragments. Opportunities remain to standardize and harmonize BNP and NT-proBNP assays, as well as to develop specific proBNP assays, to widen their clinical scope of use.

BackgroundEvaluating associations of circulating electrolytes with atrial fibrillation (AF) and burden of supraventricular arrhythmias can give insights into arrhythmia pathogenesis.MethodsWe conducted a cross-sectional analysis of 6,398 participants of the Atherosclerosis Risk in Communities (ARIC) study, ages 71-90, with data on serum electrolytes (magnesium, calcium, potassium, phosphorus, chloride, sodium). Prevalence of AF was determined from study 12-lead electrocardiograms and prior history of AF-related hospitalizations. A subset of 317 participants also underwent electrocardiographic recordings for up to 14 days using the Zio®patch. Burden of other supraventricular arrhythmias [premature atrial contractions (PACs), supraventricular tachycardia] was determined with the Zio®patch. We used multivariable logistic and linear regression adjusting for potential confounders to determine associations of electrolytes with arrhythmia prevalence and burden.ResultsAmong 6,394 eligible participants, 614 (10%) had prevalent AF. Participants in the top quintiles of magnesium [odds ratio (OR) 0.82, 95% confidence interval (CI) 0.62, 1.08], potassium (OR 0.82, 95%CI 0.68, 1.00), and phosphorus (OR 0.73, 95%CI 0.59, 0.89) had lower prevalence of AF compared to those in the bottom quintiles. No clear association was found for circulating chloride, calcium or sodium. Higher concentrations of circulating calcium were associated with lower prevalence of PACs using a standard 12-lead electrocardiogram, while higher concentrations of potassium, chloride and sodium were associated with higher PAC prevalence. Circulating electrolytes were not significantly associated with the burden of PACs or supraventricular tachycardia among a subset of 317 participants with extended electrocardiographic monitoring.ConclusionConcentrations of circulating electrolytes present complex associations with selected supraventricular arrhythmias. Future studies should evaluate underlying mechanisms.

Background The ADAMS™ HA-8180V is the 8th generation of a fully automated ion-exchange HPLC system from ARKRAY, and the first to be released onto the US market. We evaluated the HA-8180V, for routine hemoglobin A1c measurement in comparison with the Roche Cobas c501, the Tosoh G8 analyzer for normal hemoglobin, and with the Trinity analyzer for hemoglobin variants. Methods The analytical performance (linearity, precision, carryover, and sample stability) was assessed based on the Clinical and Laboratory Standards Institute (CLSI) and manufacturer guidelines. A comparison of the HA-8180V against two major analytical methods was performed for 100 whole blood samples. HA-8180V variant mode was also compared against the Trinity ultra2 A1c analyzer for 50 samples containing hemoglobin variants (HbC 14, HbS 14, HbD 12, and HbE 10). Results The within-run and total CVs were Conclusion The eighth generation ADAMS HA-8180V A1c analyzer demonstrated high analytical performance adequate for routine clinical use.

High-sensitivity troponin T (hsTnT), a marker of CVD, and N-Terminal pro B-Type Natriuretic Peptide (NT-proBNP), a marker of heart failure, have not been widely studied in type 1 diabetes. We thus assessed the ability of these markers to independently predict CVD and MACE in a cohort with childhood-onset T1D (n=583, mean age 29 and duration 21 years) during a median follow-up of 21 years. CVD was defined as CVD death, myocardial infarction, revascularization, angina, or ischemia, and MACE as CVD death, myocardial infarction, or stroke. hsTnT and NT-proBNP were assessed with electrochemiluminescence immunoassays. Median hsTnT was 5.0 ng/L (IQR: 2.0, 10.0) and median NT-proBNP was 22.0 pg/mL (7.0, 61.0). In Cox proportional hazards models allowing for diabetes duration, gender, BMI, smoking status, HbA1c, hypertension status, HDL and non-HDL cholesterol, white blood cell count, estimated glomerular filtration rate and albumin excretion rate, both log hsTnT (HR=1.30, 95% CI: 1.06-1.59) and log NT-proBNP (HR=1.29, 95% CI: 1.13-1.48) independently predicted CVD. However, the prediction of CVD between models with and without these two markers improved only marginally (Uno’s concordance statistic p=0.06). Furthermore, log hsTnT was a slightly weaker predictor of MACE (HR=1.22, 95% CI: 0.97-1.55) compared with log NT-proBNP (HR=1.28, 95% CI: 1.11-1.47). The addition of these two markers to models already including traditional risk factors did not enhance MACE prediction (p=0.39). In conclusion, although hsTnT and NT-proBNP independently predicted both CVD and MACE, they marginally increased the area under the curve only for CAD in this type 1 diabetes cohort. Disclosure T. Costacou: None. A.K. Saenger: None. T.J. Orchard: Consultant; Self; Boehringer Ingelheim International GmbH. Funding National Institutes of Health (DK34818); Rossi Memorial Fund

Background A laboratory investigation was initiated after a renal failure patient had a 2.18 mg/dL decrease in serum creatinine , which was not explained through medical intervention. The investigation revealed specimens providing questionably low results had been collected from a peripherally inserted central catheter (PICC) line. Methods Patient specimens and serum pools were analyzed by the Siemens Vista enzymatic creatinine measurement procedure. A simulation of the patient's infusion protocol examined potential PICC line carryover and specimen collection technique. Results A simultaneously collected specimen set, arterial line and PICC line, yielded a difference of 1.86 mg/dL. Infusion and collection simulation studies suggested the most likely scenario was the infusion pump was not shut off while the specimen collection occurred and contaminated the specimen. Conclusion Providers should be aware of erroneously low creatinine results when administering catecholamine drugs and collecting specimens through the same catheter. The mechanism of specimen contamination is consistent with a siphoning effect from one lumen to the other during collection with the infusion pumps still running.

The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) formed a Task Force on the Application of Cardiac Bio-markers (TF-CB) in 2008, re-designated in 2018 as a committee (C-CB), to produce educational materials on cardiac biomarkers. Established in June 2017, definitive tables covering the majority of high-sensitivity, contemporary and point-of-care (POC) cTn assays have been developed by the C-CB and are available on the IFCC website. These tables provide extensive information about assays’ analytical characteristics and encompass information on diagnostic discriminants, particularly the 99th percentiles, as provided by the manufacturers.

The IFCC Committee on Clinical Applications of Cardiac Bio-Markers (C-CB) has directives and initiatives focused on providing evidence-based educational resources to aid and improve understanding around key analytical and clinical aspects of cardiac biomarkers used in clinical practice and the research setting. As a task force, we have previously published position statements and recommendations focused on use and analytical aspects of high-sensitivity cardiac troponin assays. The current educational document is the first from the C-CB highlighting important biochemical, analytical, and clinical aspects as they relate to the natriuretic peptides (NPs), including B-type natriuretic peptide (BNP) and N-terminal pro–B-type natriuretic peptide (NT-proBNP), with a focus on heart failure.

INTRODUCTION Glomerular hyperfiltration has long been considered to be a major contributing factor to the development of diabetic kidney disease but most studies assessed increased albumin excretion rather than reduced GFR as an outcome. To address whether early glomerular hyperfiltration results in subsequent increased risk of clinically significant loss of GFR, namely Stage 3 CKD (eGFR

Two interferences recently brought to the forefront as patient safety issues include hemolysis (hemoglobin) and biotin (vitamin B7). The International Federation for Clinical Chemistry Committee on Cardiac Biomarkers (IFCC-CB) obtained input from a majority of cTn and NP assay manufacturers to collate information related to high-sensitivity (hs)-cTnI, hs-cTnT, contemporary, and POC cTn assays, and NP assays interferences due to hemolysis and biotin. The information contained in these tables was designed as educational tools to aid laboratory professionals and clinicians in troubleshooting cardiac biomarker analytical results that are discordant with the clinical situation. Keywords: biotin; hemolysis; interferences; natriuretic peptide; troponin Cardiac troponin I and T (cTnI, cTnT) and the natriuretic peptides (NP; B-type natriuretic peptide, BNP; N Terminal-proBNP; NT-proBNP) are the primary cardiac biomarkers utilized in the diagnosis of myocardial injury and infarction (MI) and heart failure (HF), respectively. As with any clinical laboratory test, there are exogenous and endogenous factors that adversely interfere with the analytical performance of the cTn and NP assays, potentially resulting in inappropriate clinical interpretation of the results if the interferences are not identified. Analytical interferences are particularly concerning when dealing with cardiac biomarker assays, which are utilized to make time sensitive critical clinical decisions. Two interferences recently brought to the forefront as patient safety issues include hemolysis (hemoglobin) and biotin (vitamin B7, vitamin H, coenzyme R). The International Federation for Clinical Chemistry Committee on Cardiac Biomarkers (IFCC-CB) obtained input from a majority of cTn and NP assay manufacturers to collate information related to high-sensitivity (hs)-cTnI, hs-cTnT, contemporary, and POC cTn assays (Table 1) [1], and NP assays (Table 2) [2] interferences due to hemolysis and biotin. The information contained in these tables was designed as educational tools to aid laboratory professionals and clinicians in troubleshooting cardiac biomarker analytical results that are discordant with the clinical situation.

Systemic mastocytosis (SM) is a disorder characterized by the excessive accumulation of clonally derived mast cells in various tissues. When triggered, mast cells release large amounts of histamine, prostaglandins and leukotrienes. Leukotriene E4 (LTE4) is the primary stable metabolite of total cysteinyl leukotrienes. We hypothesized that secretion of LTE4 would be increased in SM and could be used alone or in combination with current urinary biomarkers to optimize screening for SM.LTE4 was measured by liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Analytical assay validation was performed using residual urine specimens. LTE4 results were normalized to urine creatinine for clinical use. Reference interval was established using a healthy volunteer cohort. Clinical sensitivity and specificity for SM detection were determined by measuring urinary biomarkers (LTE4, N-methyl histamine [NMH] and 11β-prostaglandin F2α [BPG]) in a cohort of 409 patients referred to allergy specialists, 66 (16%) of which were diagnosed with SM.Urinary LTE4 measurement was accurate, precise and linear across a range of 31-3020pg/mL. The 95th percentile of the reference interval population was104pg/mg creatinine. Median urine LTE4 concentrations were significantly higher among patients with SM (97pg/mg cr. vs. 50pg/mg cr.; p0.01). Elevated urinary LTE4 was 48% sensitive and 84% specific for SM. Clinical sensitivity was 53% for BPG (1000ng/mL) and 71% for NMH (200ng/mL). Incorporating all three urinary metabolites improved the SM diagnostic sensitivity to 97%, with minimal change in specificity.We have developed a sensitive and precise LC-MS/MS assay for quantitation of LTE4 in urine. Incorporating LTE4 into a panel including BPG and NMH provides a much-needed screening tool for a complicated disease with non-specific symptoms and invasive confirmatory testing.

Background B-Type natriuretic peptides (BNP) and cardiac troponin T (cTnT) predict cardiovascular events in heart failure (HF) patients, but additional refinement in risk stratification may be possible by targeting pathways leading to fibrosis. We aimed to assess the value of serial measurements of soluble suppression of tumorigenicity 2 (sST2) and galectin-3 to identify risk for adverse pathophysiologic processes. Methods New York Heart Association (NYHA) functional class III–IV HF patients (n = 180; LVEF ≤40%) were prospectively evaluated with biomarkers collected every 3 months over 2 years and analyzed regarding a primary end point of death/cardiac transplantation and a secondary end point of HF-related hospitalization or death/transplantation. Results Time-dependent univariate analyses demonstrated that elevations of sST2 (≥49.3 ng/mL male, ≥33.5 ng/mL female) and galectin-3 (≥22.1 ng/mL) were predictive of the primary and secondary end points. In multivariate models adjusted for BNP, cTnT, and clinical variables, sST2 but not galectin-3 remained an independent predictor (hazard ratio 3.22, 95% confidence interval 1.76–5.89; P Conclusions Serial monitoring of sST2 (indicating myocardial fibrosis and remodeling) and cTnT (reflecting myocardial injury) identifies highest-risk HF outpatients and may be valuable to guide patient tailored therapy during follow-up evaluations. Serial galectin-3 monitoring in ambulatory HF patients may not be of benefit.

Objectives: Lipoprotein-associated phospholipase A2 (Lp-PLA 2 ) is increased in circulation in patients at higher risk of coronary heart disease (CHD) events and stroke. Therefore, measurement of Lp-PLA 2 can be used as an adjunct to traditional cardiovascular risk factors for identifying individuals at higher risk of cardiovascular events. Recently, a reagent for measuring Lp-PLA 2 activity (diaDexus, San Francisco, CA) received FDA approval. Here we evaluate the assay performance of the Lp-PLA 2 activity assay. Methods: Lp-PLA 2 activity assay reagent performance was evaluated on an open user-defined channel on a Cobas 6000/c501 (Roche Diagnostics, Indianapolis, IN) using a 5-point calibration curve (0–400 nmol/min/mL). Analytical performance was established for the following parameters: precision, linearity, accuracy, analytical sensitivity, analytical specificity, reference interval, reagent lot-to-lot comparison, specimen type, on-board reagent stability, and sample stability. Results: Assay limit of detection was determined to be 7.8 nmol/min/mL with an average %CV of 2.8%. Precision studies revealed a coefficient of variation ≤ 1.6% between 79 and 307 nmol/min/mL and accuracy was demonstrated between 4.8–368.7 nmol/min/mL. Comparable results were generated in paired SST serum and EDTA plasma. No age association was found with Lp-PLA 2 activity at the 95th percentile however a gender association was identified resulting in gender-specific 95th percentile limits in a healthy reference population. No bias was found when comparing results from several different lots of assay reagent. Lp-PLA 2 activity results are extremely stable in both serum and EDTA plasma under refrigerate and frozen storage conditions up to 31 days. Conclusions: Lp-PLA 2 activity assay displays accurate and precise performance characteristics on the Cobas c501 platform. The assay performance is significantly improved over the predecessor immunoassay allowing for adoption of Lp-PLA 2 activity in clinical practice.

Cardiac troponin (cTn) testing has evolved significantly in recent times. Because of increased sensitivity, its use has shifted from a marker used to help diagnose acute myocardial infarction (MI) to a marker than can be used in the outpatient setting, as well as for both detection of myocardial injury and risk-stratification. Its main role remains in the diagnosis of acute MI and the risk-stratification of patients presenting with suspected acute coronary syndrome. The analytical improvements in assays leading to precise high-sensitivity cTn assays have contributed to the development of numerous strategies to identify patients at both low- and high-risk for acute MI within a few hours. These approaches should reduce overcrowding in the emergency room and expedite triaging. The ability of measuring cTn in most patients using high-sensitivity (hs) assays has allowed for the opportunity to examine its use in the detection of cardiotoxicity in patients undergoing chemotherapy, as well as exploring the application in both primary and secondary prevention of coronary artery disease. This particular field of research has become increasingly complex, partly due to the numerous cTn assays available (I and T; point-of-care, contemporary, hs) and an array of approaches in which one can use the test. The purpose of this document is to summarize the analytical and clinical information relevant to cTn assays, in particular, hs-cTn assays, and describe present and future opportunities for use of cTn in acute cardiac care and in the outpatient setting.

Background: Complete blood counts (CBCs) are commonly obtained in large multicenter studies. We assessed the stability of 10 parameters after short-term (up to 30 days) frozen storage. Methods: We compared CBC measurements from fresh samples (n = 53) with samples stored for up to 30 days at −70 °C. We calculated the CVs and intraclass correlation coefficients. Results: Mean values of most parameters, with the exception of hemoglobin and platelet count, were significantly different by 15 days of storage. White blood cell count (CV, 38.3%; 95% CI, 31.3%–46.2%) and red cell distribution width (CV, 37.7%; 95% CI, 34.1%–41.3%) were the most variable. After 30 days, only hemoglobin remained stable and reliable (CV, 0.8%; 95% CI, 0.4%–1.3%). Conclusions: Hemoglobin remained stable in frozen blood samples stored for up to 30 days at −70 °C and may be reliably used in research studies using short-term frozen specimens. Other CBC parameters measured in stored blood are not sufficiently reliable for research or patient care.

We investigated residual beta cell function in participants from the DCCT/EDIC study with an average of 35 (range 27, 48) years duration of T1D. Between 2015-2017 after 22-24 years of follow-up in EDIC, a 4-hour mixed meal tolerance test was administered to 944 participants and 7 timed plasma specimens were collected and assayed for C-peptide using a chemiluminescent immunoassay (Roche). We defined a significant post-stimulus response as a peak C-peptide concentration >0.03 nmol/L, based on an earlier DCCT study which demonstrated that the risk of microvascular disease progression was markedly higher among participants who entered the trial with values below this concentration. Overall, 71 (7.5%) participants were classified as “responders” with a median peak C-peptide of 0.10 nmol/L (IQR 0.06, 0.15). Among the 873 participants classified as “non-responders”, 46 had detectable peak C-peptide between 0.003 (limit of detection) and 0.029 nmol/L. Responders were slightly older than non-responders (58.5 ± 6.2 vs. 56.5 ± 6.8 y; p=0.02), yet had similar age of onset of diabetes (22.5 ± 7.0 vs. 21.4 ± 7.8 y) and duration of diabetes (35.9 ± 5.1 vs. 35.0 ± 4.9 y). Compared to non-responders, responders had lower HbA1c values (8.6 ± 1.7 vs. 8.9 ± 1.5%; p=0.01) and higher stimulated C-peptide (0.22 ± 0.14 vs. 0.11 ± 0.11 nmol/L; p In conclusion, beta cell function persists in some very long duration T1D patients and is associated with clinically meaningful reductions in the frequency of severe hypoglycemia. Disclosure R. Gubitosi-Klug: None. B. Braffett: None. S.M. Hitt: None. V. Arends: None. M. Steffes: None. A.K. Saenger: Advisory Panel; Self; Alere Inc. J. Lachin: Board Member; Self; AbbVie Inc., Celgene Corporation. J.P. Palmer: None.

OBJECTIVE Women with type 1 diabetes have increased risk of infertility compared to women without diabetes even after adjustment for irregular menses, but aetiologies are incompletely understood. Our aim was to examine the prevalence of abnormalities in ovarian markers consistent with polycystic ovary syndrome in women with type 1 diabetes and associations with irregular menses and diabetes-specific variables. DESIGN, PATIENTS AND MEASUREMENTS We conducted a secondary analysis of women in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC), a randomized trial and observational follow-up of intensive insulin therapy for type 1 diabetes. We included women with anti-Mullerian hormone (AMH) measurements among women not using oral contraceptives (n = 187). Initial AMH and testosterone measures were performed between EDIC years 1 and 4. History of irregular menses was assessed annually. RESULTS The median age of women was 35 (interquartile ratio 29, 40) years; 133 (35%) had elevated AMH and 62 (17%) reported irregular menses. Twelve per cent of women had relative elevations in total testosterone. In multivariable models, lower insulin dosages were associated with higher AMH concentrations (P = .0027), but not diabetes duration, glycemic control, body mass index or irregular menses. Neither irregular menses nor diabetes-specific variables were associated with testosterone concentrations. CONCLUSIONS Among women with type 1 diabetes in their thirties, abnormalities in ovarian markers are common and not associated with irregular menses and thus may partially account for decreased fecundity in women with type 1 diabetes.

Objectives We hypothesized significant gaps remained for cardiac troponin (cTn) utilization in the United States, despite an emerging evidence base and guideline recommendations. We tested this hypothesis and investigated differences and trends between the use of cTn in adult versus pediatric hospitals. Design and methods Individuals were identified by a targeted distribution through personal contact and professional society email lists. Participants completed an online survey (Qualtrics) from 07/15/13 to 07/26/13. The 31-item questionnaire used skipped logic and collected data about the respondent and their institutional cTn clinical practices. Data tabulation and analysis were conducted using Qualtrics and Microsoft Excel. Results A total of 159 unique laboratories responded to the survey, representing primarily adult (81%) versus pediatric (19%) institutions. 59% of laboratories utilize the guideline recommended 99th percentile as the upper reference limit (URL) for cTn, with large variability in reporting practices among users of the same assay. 73% of laboratories reported simultaneous ordering of other cardiac biomarkers with cTn, a majority which included CK-MB. Interpretive comments were used with cTn in 71 laboratories with a significant amount of heterogeneity. Pediatric hospitals reported a lower frequency of cTn orders and were less likely to consider elevated cTn a critical value. Conclusions Gaps in current utilization and reporting of cTn exist, along with practices inconsistent with clinical guideline recommendations. Implementation of the 99th percentile and serial sampling protocols will be critical to adoption of high-sensitivity cTn assays. Differences in chest pain etiology are the most likely reason for the notable differences between cTn use in adults versus pediatric hospitals.

The use of soluble cardiac biomarkers such as N-terminal pro-brain natriuretic peptide (NT-proBNP) and troponin has revolutionized prognostication for patients with AL amyloidosis. Soluble ST2 (sST2) and galectin-3 have also been reported to have prognostic value in other cardiac patient populations. We identified 502 patients with AL amyloidosis, who provided a research sample and consent to review their medical records between 1/1/2006-12/31/2010 within 90 days of their diagnosis. Samples were assayed for sST2 and galectin-3. Within this AL amyloidosis population, overall survival (OS) was 25.5 months (95% CI 18, 35.7 months). Receiver operating curve analyses were done to detect the best cut-points for sST2 and galectin-3 to predict both 1- and 5-year OS. The respective cut points for sST2 were 30 and 29.7 ng/mL, while the median sST2 for the entire population was 31 ng/mL (IQR 19.8, 53.6). The respective cut points for galectin-3 were 11 and 10.4 ng/mL while the median for the entire population was 16.6 ng/mL (IQR 11.5, 24.0). Although on univariate analysis, both sST2 and galectin-3 were prognostic, upon multivariate analysis, only sST2 was independent of troponin, NT-proBNP, serum immunoglobulin free light chain, and blood pressure. Not only did sST2 add to previously reported prognostication systems, but a novel prognostication 5-point system including sST2 was possible. The addition of sST2 - but not galectin-3 - to existing prognostication systems for patients with AL amyloidosis strengthens the ability to predict for death.

Objectives Nuclear magnetic resonance (NMR) spectroscopy has been successfully applied to the measurement of high-density lipoprotein (HDL) particles, providing particle concentrations for total HDL particle number (HDL-P), HDL subclasses (small, medium, large) and weighted, average HDL size for many years. Key clinical studies have demonstrated that NMR-measured HDL-P was more strongly associated with measures of coronary artery disease and a better predictor of incident cardiovascular disease (CVD) events than HDL-cholesterol (HDL-C). Recently, an NMR-based clinical analyzer, the Vantera®, was developed to allow lipoprotein measurements to be performed in the routine, clinical laboratory setting. The aim of this study was to evaluate and report the performance characteristics for HDL-P quantified on the Vantera® Clinical Analyzer. Design and methods Assay performance was evaluated according to Clinical and Laboratory Standards Institute (CLSI) guidelines. In order to ensure that quantification of HDL-P on the Vantera® Clinical Analyzer was similar to the well-characterized HDL-P assay on the NMR profiler, a method comparison was performed. Results The within-run and within-lab imprecision ranged from 2.0% to 3.9%. Linearity was established within the range of 10.0 to 65.0 μmol/L. The reference intervals were different between men (22.0 to 46.0 μmol/L) and women (26.7 to 52.9 μmol/L). HDL-P concentrations between two NMR platforms, Vantera® Clinical Analyzer and NMR Profiler, demonstrated excellent correlation ( R 2 = 0.98). Conclusions The performance characteristics, as well as the primary tube sampling procedure for specimen analysis on the Vantera® Clinical Analyzer, suggest that the HDL-P assay is suitable for routine clinical applications.

Background Biochemical analysis of body fluids may lend insight into the pathogenesis of disease. Most commercially-available clinical laboratory methods are intended for blood-derived specimens and/or urine and laboratories must characterize the analytical performance of these methods for other specimen types such as body fluids. The aim of this work is to demonstrate one approach for characterizing analytical performance of assays for clinical analysis of body fluids. Methods Residual waste samples were obtained from clinically ordered testing. Validation studies were performed for 8 chemistry analytes on Roche Cobas 6000 c501 (Roche Diagnostics, Inc.) analyzers. Accuracy, precision, analytical measurable range, reportable range, analytic sensitivity, interferences, analyte stability were assessed. Laboratory workflow for body fluid handling was designed based on results obtained. Results Sample matrix interferences were not observed for the body fluids tested and assay reportable ranges used for serum were validated for body fluids. Dilution of body fluid specimens with saline demonstrated non-linear recovery of some enzyme activities . Assay imprecision was comparable to the manufacturer's claims for serum. The serum index thresholds for interference from hemoglobin and lipemia were lower for body fluids compared to manufacturer's stated limits for serum. Pretreatment of body fluid samples with hyaluronidase caused a 28% false increase in lipase activity, and 13% increase in total protein concentration. Ambient temperature analyte stability in body fluids was ≤24 h for most analytes compared to manufacturer's stated stability of 7 days for serum. In contrast to serum, lactate dehydrogenase (LDH) was labile in frozen body fluid specimens. Conclusions Validation of analytical methods for body fluid testing is a necessary exercise to exclude potential matrix effects and set pre-analytic specimen quality criteria.

BACKGROUND There is growing interest in fructosamine, glycated albumin, and 1,5-anhydroglucitol (1,5-AG) as alternative measures of hyperglycemia, particularly for use in settings where traditional measures (glucose and HbA1c) are problematic or where intermediate (2–4 weeks) glycemic control is of interest. However, reference intervals for these alternative biomarkers are not established. METHODS We measured fructosamine, glycated albumin, and 1,5-AG in a community-based sample of US black and white adults who participated in the Atherosclerosis Risk in Communities (ARIC) Study. We calculated reference intervals, evaluated demographic differences, and derived cutoffs aligned with current diagnostic cutpoints for HbA1c and fasting glucose. RESULTS In a healthy reference population of 1799 individuals (mean age, 55 years; 51% women; 15% black), the 2.5 and 97.5 percentiles, respectively, were 194.8 and 258.0 μmol/L for fructosamine, 10.7% and 15.1% for glycated albumin, and 8.4 and 28.7 μg/mL for 1,5-AG. Distributions differed by race, sex, and body mass index. Equivalent concentrations of fructosamine and glycated albumin corresponding to an HbA1c of 6.5% (96.5 percentile) were 270.2 μmol/L and 15.6%, respectively. Equivalent concentrations of fructosamine and glycated albumin corresponding to a fasting glucose of 126 mg/dL (93.9 percentile) were 261.7 μmol/L and 15.0%, respectively. CONCLUSIONS The reference intervals for these biomarkers should inform their clinical use. Diagnostic cutpoint equivalents for fructosamine and glycated albumin could be useful to identify persons with hyperglycemia in settings where fasting glucose or HbA1c are not available or where the interpretation of these traditional measures is problematic.

Acute coronary syndrome (ACS) encompasses a pathophysiological spectrum of cardiovascular diseases, all of which have significant morbidity and mortality. ACS was once considered an acute condition; however, new treatment strategies and improvements in biomarker assays have led to ACS being an acute and chronic disease. Cardiac troponin is the preferred biomarker for the diagnosis of myocardial infarction, and there is considerable interest and efforts toward development and implementation of high-sensitivity cardiac troponin (hs-cTn) assays worldwide. Analytical and clinical performance characteristics of hs-cTn assays as well as testing limitations are important for laboratorians and clinicians to understand in order to utilize testing appropriately. Furthermore, expanding the clinical utility of hs-cTn into other cohorts such as asymptomatic community dwelling populations, heart failure, and chronic kidney disease populations supports novel opportunities for improved short- and long-term prognosis.

BACKGROUND Aggressive LDL cholesterol (LDL-C)-lowering strategies are recommended for primary and secondary prevention of cardiovascular events. A newly derived equation for LDL-C estimation was recently published that addressed limitations in the commonly used Friedewald LDL-C calculation method. The novel method was reported to classify patients with superior concordance to measured LDL-C compared to the Friedewald method, particularly in patients with LDL-C METHODS We evaluated the performance of the novel method within an independent cohort of 23 055 patients with LDL-C measured by the gold standard β-quantification reference method. RESULTS Overall Friedewald underestimated and the novel method overestimated measured LDL-C. Both estimations significantly deviated from the reference method when LDL-C was 70 mg/dL compared to the Friedewald equation. CONCLUSIONS We compared both novel and Friedewald estimated LDL-C against the LDL-C reference method; in contrast, the prior study relied on validation of a subset of samples by β-quantification to allow the use of the vertical autoprofile method for LDL-C measurement. We conclude that the novel method has some benefits but it is unclear whether improvements over the Friedewald calculation are substantive enough to justify making the change in routine clinical practice and to improve patient outcomes.

Context.— Systems-based practice (SBP) is 1 of 6 core competencies required in all resident training programs accredited by the Accreditation Council for Graduate Medical Education. Reliable methods of assessing resident competency in SBP have not been described in the medical literature.Objective.— To develop and validate an analytic grading rubric to assess pathology residents' analyses of SBP problems in clinical chemistry.Design.— Residents were assigned an SBP project based upon unmet clinical needs in the clinical chemistry laboratories. Using an iterative method, we created an analytic grading rubric based on critical thinking principles. Four faculty raters used the SBP project evaluation rubric to independently grade 11 residents' projects during their clinical chemistry rotations. Interrater reliability and Cronbach α were calculated to determine the reliability and validity of the rubric. Project mean scores and range were also assessed to determine whether the rubric differentiated resident critical thinking skills related to the SBP projects.Results.— Overall project scores ranged from 6.56 to 16.50 out of a possible 20 points. Cronbach α ranged from 0.91 to 0.96, indicating that the 4 rubric categories were internally consistent without significant overlap. Intraclass correlation coefficients ranged from 0.63 to 0.81, indicating moderate to strong interrater reliability.Conclusions.— We report development and statistical analysis of a novel SBP project evaluation rubric. The results indicate the rubric can be used to reliably assess pathology residents' critical thinking skills in SBP.

Objective: Familial hypercholesterolemia (FH) can be due to mutations in LDLR, PCSK9, and APOB. In phenotypically defined patients, a subset remains unresponsive to lipid-lowering therapies and requires low density-lipoprotein (LDL) apheresis treatment. In this pilot study, we examined the genotype/phenotype relationship in patients with dyslipidemia undergoing routine LDL apheresis. Design: LDLR, APOB, and PCKS9 were analyzed for disease-causing mutations in seven patients undergoing routine LDL apheresis. Plasma and serum specimens were collected pre- and post-apheresis and analyzed for lipid concentrations, Lp(a) cholesterol, and lipoprotein particle concentrations (via NMR). Results: We found that four patients harbored LDLR mutations and of these, three presented with xanthomas. While similar reductions in LDL-cholesterol (LDL-C), apolipoprotein B, and LDL particles (LDL-P) were observed following apheresis in all patients, lipid profile analysis revealed the LDLR mutation-positive cohort had a more pro-atherogenic profile (higher LDL-C, apolipoprotein B, LDL-P, and small LDL-P) pre-apheresis. Conclusion: Our data show that not all clinically diagnosed FH patients who require routine apheresis have genetically defined disease. In our small cohort, those with LDLR mutations had a more proatherogenic phenotype than those without identifiable mutations. This pilot cohort suggests that patients receiving the maximum lipid lowering therapy could be further stratified, based on genetic make-up, to optimize treatment. J. Clin. Apheresis 29:256–265, 2014. © 2014 Wiley Periodicals, Inc.

Objectives The aim of this study was to assess the performance of two point of care (POC) devices for capillary lipid screening in fasting and post-prandial adults. Design and methods Fasting and post-prandial capillary whole blood samples collected from 57 adult donors were analyzed simultaneously on Cholestech LDX Lipid Profile (Alere San Diego, Inc., San Diego, CA) cassettes and CardioChek Lipid Panel (Polymer Technology Systems, Indianapolis, IN) strips. Paired serum samples were collected from the same donors and analyzed with CDC-certified methods for total cholesterol, high density lipoprotein cholesterol (HDL-C) and non-blanked triglycerides. Non-HDL-C (total cholesterol minus HDL-C) and low density lipoprotein cholesterol (LDL-C) were calculated. Mean bias between capillary whole blood and serum laboratory lipids was calculated. Results HDL-C measurements were not affected by triglyceride content on either device. However, both devices exhibited significant variability in triglyceride measurement relative to the reference method. Compared to reference methods, Cholestech was more accurate than CardioChek for non-HDL-C while CardioChek was more accurate for HDL-C. Among the calculated cardiovascular risk parameters (LDL-C and non-HDL-C), Cholestech-calculated non-HDL-C exhibited the least average bias in both fasting and postprandial samples. Conclusions The optimal approach to capillary lipid screening may be to use Cholestech non-HDL cholesterol; as it exhibited little bias relative to CDC reference methods in both fasting and postprandial samples, facilitating lipid screening in non-fasting adults.

Altered concentrations of bile acid (BA) in the colon can cause diarrhea or constipation. More than 25% of patients with irritable bowel syndrome with diarrhea or chronic diarrhea in Western countries have BA malabsorption (BAM). As BAM is increasingly recognized, proper diagnostic methods are needed to help direct the most effective course of treatment for the chronic bowel dysfunction. We review the methodologies, advantages, and disadvantages of tools that directly measure BAM: the 14 C-glycocholate breath and stool test, the 75 selenium homotaurocholic acid test (SeHCAT), and measurements of 7 α-hydroxy-4-cholesten-3-one (C4) and fecal BAs. The 14 C-glycocholate test is laborious and no longer widely used. The 75 SeHCAT has been validated but is not available in the United States. Measurement of serum C4 is a simple and accurate method that can be used for most patients but requires further clinical validation. Assays to quantify fecal BA (total and individual levels) are technically cumbersome and not widely available. Regrettably, none of these tests are routinely available in the United States; assessment of the therapeutic effects of a BA binder is used as a surrogate for diagnosis of BAM. Recent data indicate the advantages to studying fecal excretion of individual BAs and their role in BAM; these could support the use of the fecal BA assay, compared with other tests. Measurement of fecal BA levels could become a routine addition to the measurement of fecal fat in patients with unexplained diarrhea. Availability ultimately determines whether the C4, SeHCAT, or fecal BA test is used; more widespread availability of such tests would enhance clinical management of these patients.

BACKGROUND Aspirin's therapeutic action is via inhibition of platelet cyclooxygenase 1 (COX-1) thromboxane A2 (TxA2) production. The aim of this study was to evaluate TxA2 production, in the absence of platelet COX-1 activity, in coronary atherosclerotic heart disease patients with and without atherothrombotic myocardial infarction (MI). METHODS AND RESULTS TxA2 production, in the absence of platelet COX-1 activity, was evaluated in 44 patients taking aspirin on 3 commercially available assays that detect metabolites of TxA2 in the urine. Two assays measure urine 11-dehydro-thromboxane B2 (TxB2) alone and 1 measures urine 11-dehydro-TxB2 plus 11-dehydro-2,3-dinor-TxB2. Platelet COX-1 inhibition was confirmed on

Measuring lipoprotein-associated phospholipase AA total of 24 healthy individuals (22-47years of age) were prospectively collected at several time points: daily for five days (after overnight fast), daily for three days (while non-fasting), weekly for four weeks (after overnight fast), and monthly for 6months (after overnight fast). Intra-individual and inter-individual variability was determined. The index of individuality (IoI) and reference change value (RCV) were calculated for each time period.Variability in Lp-PLA