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Background: Traditional or reference methods represent a basis and foundation for microbiological analysis, however the need to implement new techniques that minimize the time, reduce errors, optimize economic resources and ensure the veracity and accuracy of the results is evident. Aerobic mesophilic microorganisms are facultative aerobic or anaerobic bacteria, wich ferment glucose and other sugars. On the control of quality food, Mesophilic counts play a key role when determining aspects such as hygiene, temperature control, product life, contaminated raw material, poor storage, among others. Objetives: To compare time of analysis, cost effectiveness, reproducibility, reliability and accuracy in the results of the traditional method of mesophilic vs PetrifilmTM sheet method for mesophilic counts Methods: PetrifilmTM sheet method validation is performed as indicated in the ISO 16140 standard or its equivalent the NTC 5014. Artificially contaminated product (Bacon, sausage and mortadella) from a 1.0 MacFarland pattern, in order to obtain low charge (1 to 10 CFU), average (10 to 100 CFU) and high (100 to 1000 CFU). The samples were analyzed from the processing of two analysts, with 20 replicates per sample Results: For the test of inclusivity, both techniques showed the average recovery of microorganisms tested (E. coli ATCC 25922, S. aureus ATCC 25923, Enterobacter ATCC 13048, Candida albicans ATCC 10231); the concordance of both measurements met 100%; the linear correlation was equal to 0.954, meaning that the difference between the results of the two methods analyzed is 0.046, and that for same sample counts are correlated in 95% of cases. Conclusions: It was possible to ensure the veracity of the results in a 100% sensitivity, accuracy and precision of the method before mentioned, was the uncertainty of outcomes with 95% confidence, being an efficient and effective method for controlling quality in the food industry. [ABSTRACT FROM AUTHOR]

Background: Multicenter laboratory may apply both automated flow cytometer and microscopy for urinalysis. Automated flow cytometer such as Sysmex UF-1000i evaluates particles with native urine without centrifugation and reports as "counts per μL." Microscopic examination recommended as the reference method for urine sediment analysis reports results as "counts per HPF (or μL)." Moreover, some results from flow cytometer are needed to be checked visually under microscopy. Therefore, it is worth to establish the consistency of the results from these two methods., Methods: Urine specimens from 412 patients were examined with Sysmex UF-1000i and manual microscopy using FAST-READ disposable counting chambers. White blood cell (WBC) and red blood cell (RBC) counting results from UF-1000i after transferred with the converting factor (0.297) we estimated were compared with that from microscopic examination. Method comparison was performed using Passing-Bablok analysis., Results: After transferred with the converting factor (0.297), cell counting results from UF-1000i showed a good correlation with that derived by the reference method (R 2 was 0.868 for RBCs (P < 0.001), 0.882 for WBCs (P < 0.001)). Passing-Bablok analysis showed no systematic difference (intercept estimate, -1 [95%CI, -7 to 3] and slightly proportional (slope estimate, 1.2 [95%CI, 1.0 to 1.7]) bias between concentrations of cells measured by manual microscopy and Sysmex UF-1000i using the converting factor., Conclusion: The converting factor (0.297) helps to transfer "counts per μL (non-centrifugal urine)" to "counts per μL (equal to centrifugal urine)," and to keep the urine particle analysis results of Sysmex UF-1000i consistent with the results from the reference method., (© 2019 The Authors. Journal of Clinical Laboratory Analysis Published by Wiley Periodicals, Inc.)

In an article in the Journal of Diabetes Science and Technology, Macleod and coworkers describe an evaluation of LifeScan glucose meters that focus on the effects of sample types and comparison methods. They make a valid point that these factors influence the accuracy observed in evaluations and recommend the comparison method be the one recommended by the manufacturer for the sample type in the intended use statement. Yet, the recommended comparison method is not a reference method. The accuracy hierarchy of definitive, reference, and field methods originally described by Tietz should remind one that virtually all glucose meter evaluations use commercially available field methods as the comparison method. Finally, one should not neglect the FDA adverse event database as a way to assess glucose meter performance.

Measurement of urine albumin has been introduced in the new classification of kidney disease (KD) as a marker for detecting, monitoring and predicting KD. Currently, the measure is not standardized. The variability of results obtained with commercially available procedures is important and can lead to misclassification of patients. Analytical standardization, started in 2007, is in progress. SRM 2925 primary reference material, SRM 3666 secondary reference material and liquid chromatography isotope dilution mass spectroscopy (LC-IDMS) reference measurement procedure are being validated by the National Institute of Standards and Technology (NIST). This report presents strategies and difficulties for developing this reference system.

We estimated the measurement uncertainty (MU) of platelet concentration measured using the Sysmex XN system with two reference platelet counting methods described by DIN 58932-5 (PTB method) and the International Council for Standardization in Haematology (ICSH method). Ten blood samples were used to estimate and compare the MU of the XN system, and 30 samples were used to compare the methods. The standard uncertainty of the reference method was significantly higher for the ICSH method; the PTB method showed higher platelet concentrations than the ICSH method. When applying different methods with the XN system, optic counting showed higher MU compared to the other methods. There was good correlation among the two reference methods and three automated platelet-counting methods. We evaluated the MU in platelet concentrations measured using an automated hematology analyzer. Our results suggest that using the PTB method for calculating MU of the automated hematology analyzer is superior to the ICSH method because of its lower standard uncertainty.

Background: In laboratory medicine, routine periodic analyses for internal and external quality control measurements interpreted by statistical methods are mandatory for batch clearance. Data analysis of these process-oriented measurements allows for insight into random analytical variation and systematic calibration bias over time. However, in such a setting, any individual sample is not under individual quality control. The quality control measurements act only at the batch level. Quantitative or qualitative data derived for many effects and interferences associated with an individual diagnostic sample can compromise any analyte. It is obvious that a process for a quality-control-sample-based approach of quality assurance is not sensitive to such errors., Content: To address the potential causes and nature of such analytical interference in individual samples more systematically, we suggest the introduction of a new term called the irregular (individual) analytical error. Practically, this term can be applied in any analytical assay that is traceable to a reference measurement system. For an individual sample an irregular analytical error is defined as an inaccuracy (which is the deviation from a reference measurement procedure result) of a test result that is so high it cannot be explained by measurement uncertainty of the utilized routine assay operating within the accepted limitations of the associated process quality control measurements., Summary: The deviation can be defined as the linear combination of the process measurement uncertainty and the method bias for the reference measurement system. Such errors should be coined irregular analytical errors of the individual sample. The measurement result is compromised either by an irregular effect associated with the individual composition (matrix) of the sample or an individual single sample associated processing error in the analytical process., Outlook: Currently, the availability of reference measurement procedures is still highly limited, but LC-isotope-dilution mass spectrometry methods are increasingly used for pre-market validation of routine diagnostic assays (these tests also involve substantial sets of clinical validation samples). Based on this definition/terminology, we list recognized causes of irregular analytical error as a risk catalog for clinical chemistry in this article. These issues include reproducible individual analytical errors (e.g. caused by anti-reagent antibodies) and non-reproducible, sporadic errors (e.g. errors due to incorrect pipetting volume due to air bubbles in a sample), which can both lead to inaccurate results and risks for patients.

Blood-based indicators that are used in the assessment of iron status are assumed to be accurate. In practice, inaccuracies in these measurements exist and stem from bias and variability. For example, the analytic variability of serum ferritin measurements across laboratories is very high (>15%), which increases the rate of misclassification in clinical and epidemiologic studies. The procedures that are used in laboratory medicine to minimize bias and variability could be used effectively in clinical research studies, particularly in the evaluation of iron deficiency and its associated anemia in pregnancy and early childhood and in characterizing states of iron repletion and excess. The harmonization and standardization of traditional and novel bioindicators of iron status will allow results from clinical studies to be more meaningfully translated into clinical practice by providing a firm foundation for clinical laboratories to set appropriate cutoffs. In addition, proficiency testing monitors the performance of the methods over time. It is important that measures of iron status be evaluated, validated, and performed in a manner that is consistent with standard procedures in laboratory medicine., (© 2017 American Society for Nutrition.)

Objectives: Microscopic leukocyte differentials display many drawbacks. Several single 5 to 8-color tubes using multiparameter flow cytometry (MFC) are able to provide extended differentials with sequential gating-based analysis strategies. We investigated a new 5-color MFC method to perform an extended 8-part differential with a simplified gating strategy., Methods: Whole blood was stained with a combination of antibodies including HLA-DR-FITC/CD19-PE/CD45-ECD/CD16-PC5 + CD71-PC5/CD5-PC7., Results: An original approach was developed to exclude debris and straightforwardly gate the cells to identify sixteen populations. Strong correlations were obtained with the analyzer for neutrophils, lymphocytes, monocytes, and eosinophils (R 2 >0.9). Abnormal cells, such as immature granulocytes and blast cells were identified with a good sensitivity and excellent correlation against cytomorphologic review (R 2 =0.66 and 0.99, respectively). The choice of HLA-DR and CD5 improved specificity for the identification of activated T-lymphocytes and some lymphoid neoplastic cells, respectively., Conclusions: Here a new cytometric differential is proposed with a robust gating strategy which may be used even by unskilled cytometrists and can be easily automated. © 2017 International Clinical Cytometry Society., (© 2017 International Clinical Cytometry Society.)

Background: Potassium is an important serum ion that is frequently assayed in clinical laboratories. Quality assurance requires reference methods; thus, the establishment of a candidate reference method for serum potassium measurements is important., Methods: An inductively coupled plasma mass spectrometry (ICP-MS) method was developed. Serum samples were gravimetrically spiked with an aluminum internal standard, digested with 69% ultrapure nitric acid, and diluted to the required concentration. The 39K/27Al ratios were measured by ICP-MS in hydrogen mode. The method was calibrated using 5% nitric acid matrix calibrators, and the calibration function was established using the bracketing method., Results: The correlation coefficients between the measured 39K/27Al ratios and the analyte concentration ratios were >0.9999. The coefficients of variation were 0.40%, 0.68%, and 0.22% for the three serum samples, and the analytical recovery was 99.8%. The accuracy of the measurement was also verified by measuring certified reference materials, SRM909b and SRM956b. Comparison with the ion selective electrode routine method and international inter-laboratory comparisons gave satisfied results., Conclusions: The new ICP-MS method is specific, precise, simple, and low-cost, and it may be used as a candidate reference method for standardizing serum potassium measurements.

In the study published in Journal of Diabetes, Science and Technology, Timothy S. Bailey and coauthors evaluated system accuracy and user performance of a new, wireless-enabled blood glucose monitoring system, the Contour Plus ONE blood glucose monitoring system. The authors declare that the study protocol was performed according to ISO 15197:2013 guidelines, in particular to clauses 6.3 and 8. Results show a high level of accuracy of the product in a laboratory setting as well as in the hands of lay users. However, differences between both study parts emerge that stimulate discussion about the used comparison method.

Introduction: To provide target values for the manufacturers' survey of the Japanese Society for Laboratory Hematology (JSLH), accurate standard data from healthy volunteers were needed for the five-part differential leukocyte count. To obtain such data, JSLH required an antibody panel that achieved high specificity (particularly for mononuclear cells) using simple gating procedures. We developed a flow cytometric method for determining the differential leukocyte count (JSLH-Diff) and validated it by comparison with the flow cytometric differential leukocyte count of the International Council for Standardization in Haematology (ICSH-Diff) and the manual differential count obtained by microscopy (Manual-Diff)., Methods: First, the reference laboratory performed an imprecision study of JSLH-Diff and ICSH-Diff, as well as performing comparison among JSLH-Diff, Manual-Diff, and ICSH-Diff. Then two reference laboratories and seven participating laboratories performed imprecision and accuracy studies of JSLH-Diff, Manual-Diff, and ICSH-Diff. Simultaneously, six manufacturers' laboratories provided their own representative values by using automated hematology analyzers., Results: The precision of both JSLH-Diff and ICSH-Diff methods was adequate. Comparison by the reference laboratory showed that all correlation coefficients, slopes and intercepts obtained by the JSLH-Diff, ICSH-Diff, and Manual-Diff methods conformed to the criteria. When the imprecision and accuracy of JSLH-Diff were assessed at seven laboratories, the CV% for lymphocytes, neutrophils, monocytes, eosinophils, and basophils was 0.5~0.9%, 0.3~0.7%, 1.7~2.6%, 3.0~7.9%, and 3.8~10.4%, respectively. More than 99% of CD45 positive leukocytes were identified as normal leukocytes by JSLH-Diff., Conclusions: When JSLH-Diff method were validated by comparison with Manual-Diff and ICSH-Diff, JSLH-Diff showed good performance as a reference method., (© 2016 John Wiley & Sons Ltd.)

The total haemoglobin (Hb) concentration in blood is one of the most frequently measured analytes in clinical medicine because of its significance for evaluating the health state of a human. The spectrophotometric cyanmethaemoglobin (HiCN) method is the internationally accepted conventional reference method to determine this biomarker. It is frequently used in clinical routine diagnostics but is not traceable to the International System of Units and thus does not meet highest metrological demands. A further critical issue is the toxicity of the necessary potassium cyanide. Different methods to solve these problems are reported here. They all were validated against the HiCN method in an interlaboratory comparison by measuring the total Hb concentration present in the certified reference material JCCRM 912-2M. Methods considered were the spectrophotometric alkaline haematin detergent (AHD) method as well as several isotope dilution (ID)-based approaches. The latter include inductively coupled plasma mass spectrometry (ICP-MS), species-specific (SS) ICP-MS, organic MS and Raman spectrometry. Graphical abstract ᅟ.

Background: Accurate measurement of gentamicin concentration in serum and plasma is required for therapeutic drug monitoring to ensure appropriate treatment of patients. In this work, we present a validated LC-MS/MS-based candidate reference measurement procedure for total gentamicin quantification to be used for standardization and harmonization of routine assays applied for therapeutic drug monitoring of this compound. Total gentamicin is the sum of the concentrations of five known congeners C1, C1a, C2, C2a and C2b. To our knowledge, there is so far no LC-MS method for quantification of total gentamicin in human serum described in literature., Methods: Sample preparation was based on sample dilution with an aqueous internal standard solution followed by protein precipitation. Stable derivatives of gentamicin-glycine congeners were prepared by chemical synthesis and used as internal standards. The primary calibration material used in this assay was characterized by NMR spectroscopy and the pattern of the gentamicin congeners was determined. The total gentamicin was reported as the sum of the congeners which were quantified individually by LC-MS/MS., Results: The method allows the measurement of total gentamicin in human serum and plasma in the concentration range of 0.1 to 12.0μg/ml with an assay imprecision of ≤6% CV and an assay accuracy between 96% and 114%. LOD and LOQ for the total gentamicin were 0.04μg/ml and 0.13μg/ml, respectively. Comparative measurement of 128 native patient samples using this method implemented at two laboratory sites showed an excellent agreement., Conclusions: Validation results proved that this protocol describes a robust and reliable method which is suggested as reference measurement procedure for the standardization and harmonization of routine assays for the quantification of total gentamicin., (Copyright © 2016. Published by Elsevier B.V.)

Background: Calcium is an important serum ion which is frequently assayed in clinical laboratories. Since quality assurance requires reference methods, the establishment of a candidate reference method for serum calcium measurement is important., Method: An inductively coupled plasma mass spectrometry (ICP-MS) method was developed. Serum samples were spiked gravimetrically with aluminum internal standard, digested with 69% ultrapure nitric acid and diluted to test concentration. Then the (44)Ca/(27)Al ratios were measured by ICP-MS in hydrogen mode. The method was calibrated using 5% nitric acid matrix calibrators and the calibration function was established with bracketing method., Results: The correlation coefficients between the measured (44)Ca/(27)Al ratios and the analyte concentrations ratios were all >0.9999. The coefficients of variation of the measurements were 0.27% and 0.16% for two spiked serum. The analytical recovery was 100.24%. The accuracy of the measurement was also verified through measurement of certified reference materials. Comparison with recognized reference method and international inter-laboratory comparisons gave satisfied results., Conclusion: New ICP-MS method is specific, precise, simple, and low in cost, and may be used as a candidate reference method in the standardization of serum calcium measurement., (Copyright © 2016. Published by Elsevier B.V.)

Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies. We also asked whether any differences among laboratories were related to the extraction and quantification methods used to determine starch and sugar concentrations. These questions were addressed by sending sub-samples collected from five woody plant tissues, which varied in NSC content and chemical composition, to 29 laboratories. Each laboratory analyzed the samples with their laboratory-specific protocols, based on recent publications, to determine concentrations of soluble sugars, starch and their sum, total NSC. Laboratory estimates differed substantially for all samples. For example, estimates for Eucalyptus globulus leaves (EGL) varied from 23 to 116 (mean = 56) mg g(-1) for soluble sugars, 6-533 (mean = 94) mg g(-1) for starch and 53-649 (mean = 153) mg g(-1) for total NSC. Mixed model analysis of variance showed that much of the variability among laboratories was unrelated to the categories we used for extraction and quantification methods (method category R(2) = 0.05-0.12 for soluble sugars, 0.10-0.33 for starch and 0.01-0.09 for total NSC). For EGL, the difference between the highest and lowest least squares means for categories in the mixed model analysis was 33 mg g(-1) for total NSC, compared with the range of laboratory estimates of 596 mg g(-1). Laboratories were reasonably consistent in their ranks of estimates among tissues for starch (r = 0.41-0.91), but less so for total NSC (r = 0.45-0.84) and soluble sugars (r = 0.11-0.83). Our results show that NSC estimates for woody plant tissues cannot be compared among laboratories. The relative changes in NSC between treatments measured within a laboratory may be comparable within and between laboratories, especially for starch. To obtain comparable NSC estimates, we suggest that users can either adopt the reference method given in this publication, or report estimates for a portion of samples using the reference method, and report estimates for a standard reference material. Researchers interested in NSC estimates should work to identify and adopt standard methods., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Aim: We have evaluated here the clinical and analytical performance of the Alere™ Heart Check (AHC) test, a rapid point-of-care immunoassay designed for the measurement of BNP from fresh capillary whole blood., Patients & Methods: One-hundred-and-sixty-three patients with stable chronic heart failure followed at the cardiac rehabilitation were submitted to simultaneous capillary (AHC) and plasma (Abbott architect system) BNP measurements., Results: Both methods showed a good correlation, although the values diverged when BNP was higher than 2000 pg/ml. Despite a relatively poor precision of AHC, however, both methods showed the same performances to assess patients' dyspnea and equivalent sensitivity, specificity, negative and positive predicting values., Conclusion: AHC BNP test is a good POC for the management of heart failure despite a relatively poor precision.

Introduction: In the modern healthcare service, patients receive care in multiple hospitals and healthcare settings. Therefore, harmonization of results from different methods and instruments, both between and within laboratories, is of the utmost importance. The present pilot study aims to test the use of a Category 1 EQA scheme across four European countries by assessing the current level of equivalence of test results., Method: This work was led by the Dutch External Quality Assurance Scheme SKML and involved 28 laboratories from three regions in the UK, Spain and Portugal, and 120 laboratories from The Netherlands. A set of six commutable samples, targeted with reference methods, were circulated and 18 biochemistry analytes were tested., Results and Conclusions: The Total Error (TE) score, defined as the probability (%) that results are within the Total Error Acceptable (TEA) limits, for the eighteen analytes was calculated. Our data show that there is a need for further harmonization of laboratory data, in particular for electrolytes (calcium, chloride, magnesium, sodium), enzymes (ALT, amylase, AST, LDH), lipids (HDL-cholesterol), and for substrates (creatinine, total protein). Lack of performance consistency between instruments was seen for most analytes. The lack of harmonization is still present despite manufacturer claims of established traceability., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Aspirin, a commonly used antiplatelet agent, blocks platelet thromboxane A₂ (TXA₂) formation from arachidonic acid (AA) by acetylating platelet cyclooxygenase-1 (COX-1). Laboratory methods currently used to detect this antiplatelet effect of aspirin provide variable results. We have reported three methods that assess platelet COX-1 acetylation (inactivation) by aspirin and its direct consequences. The first and second assays use monoclonal anti-human-COX-1 antibodies that only detect acetylated (inactivated) COX-1 and active (non-acetylated) COX-1, respectively. The third method measures platelet production of TXB₂ (the stable metabolite of TXA₂) in vitro in response to AA. We compared the results of these three reference methods with other routinely used methods for assessing the functional consequences aspirin treatment., Methods: 108 healthy volunteers were treated with low-dose aspirin for 7 days. On day 7 following aspirin treatment COX-1 in the platelets was fully acetylated whereas only non-acetylated COX-1 was present in the day 0 platelets. Further, TXB2 production by day 7 platelets was completely blocked. The following tests were performed on the samples obtained from study participants before and after seven days of aspirin treatment: PFA-100 closure time with collagen/epinephrine cartridge, VerifyNow (VN) Aspirin Assay, platelet aggregation and ATP secretion using AA, ADP, epinephrine and collagen as agonists., Results: Comparing the pre-treatment and day 7 values, methods that use AA as platelet agonist (AA-induced platelet aggregation/secretion and VN Aspirin Assay) showed high discriminative power. In contrast, results of the other tests showed considerable overlap between day 7 and day 0 values., Conclusions: Only assays that clearly distinguish between acetylated and non-acetylated platelet COX-1 are useful for establishing the antiplatelet effect of aspirin. The other tests are not suitable for this purpose., (© 2013. Published by Elsevier Ltd. All rights reserved.)