Trueness assessment of HbA1c routine assays: are processed EQA materials up to the job?

2019 ◽  
Vol 57 (10) ◽  
pp. 1623-1631 ◽  
Author(s):  
Vincent Delatour ◽  
Noémie Clouet-Foraison ◽  
Stéphane Jaisson ◽  
Patricia Kaiser ◽  
Philippe Gillery
Keyword(s):  
External Quality Assessment ◽  
Measurement Procedure ◽  
Enzymatic Assays ◽  
Clinical Specimens ◽  
Medical Laboratories ◽  
Ion Exchange Hplc ◽  
Quality Control Materials ◽  
Allowable Error ◽  
The Difference ◽  
Assay Precision

Abstract Background With the worldwide increase of diabetes mellitus prevalence, ensuring that HbA1c assays are accurate is essential. External quality assessment (EQA) programs enable laboratories to verify that analytical methods perform according to the manufacturers’ specifications. However, assessing trueness requires commutable materials, a property that is rarely characterized for EQA materials. Methods The difference in bias approach was used to assess commutability of 26 processed quality control materials for 17 of the most frequently used HbA1c assays. Involved assays included immuno-assays, enzymatic assays, affinity, ion-exchange HPLC boronate affinity HPLC and capillary electrophoresis. The measurements were performed at manufacturers or expert laboratories. Assay trueness was additionally assessed against the IFCC reference measurement procedure using fresh clinical specimens that were distributed to 450 medical laboratories. Results Commutability of processed EQA materials was highly heterogeneous and globally insufficient to rigorously assess the trueness of HbA1c assays. Using fresh clinical specimens, mean bias was −0.13 mmol/mol for low HbA1c (34 mmol/mol), between +1.0 and +1.3 mmol/mol for intermediate HbA1c (49 and 58 mmol/mol) and +1.2 mmol/mol for elevated HbA1c (90 mmol/mol). Conclusions This study demonstrates that due to insufficient commutability, most processed EQA materials are unsuitable to assess trueness of HbA1c assays and agreement between the different assays. These materials can only provide information on comparability of individual laboratory results with its peers and on assay precision. Using fresh whole blood samples, this study additionally shows that most HbA1c assays are fairly accurate and meet the total allowable error quality target of 5 mmol/mol.

scholarly journals Evaluation of Analytical Performance of Variant II Turbo HbA1c Analyzer According to Sigma Metrics

2019 ◽  
Vol 38 (1) ◽  
pp. 33-37 ◽  
Author(s):  
Giray Bozkaya ◽  
Nuriye Uzuncan ◽  
Sibel Bilgili ◽  
Ozlem Demirezen
Keyword(s):  
Quality Control ◽  
Control Measures ◽  
Analytical Performance ◽  
Major Constituent ◽  
General Evaluation ◽  
Quality Control Materials ◽  
Allowable Error ◽  
The Difference ◽  
Analytical Variation

Summary Background: Hemoglobin A1c, (HbA1c) which is the major constituent of glycated hemoglobin, has been used in the follow-up of retrospective glycemia for years and in the diagnosis of diabetes mellitus nowadays. Since the analytical performance of HbA1c should be high likewise all laboratory tests, various quality control measures are used. Sigma metrics is one of these measures and it is the combination of bias, precision and total allowable error that ensures a general evaluation of analytical quality. The aim of our study was to evaluate the analytical performance of Bio-Rad’s Variant Turbo II HbA1c analyzer according to sigma metrics. Methods: Sigma levels were calculated using the data obtained from two levels of internal and 12 external quality control materials (Bio-Rad) of Variant II Turbo HbA1c analyzer according to s= (TEa% - Bias%) / CV% formula. Results: The mean sigma levels for low and high quality control materials were found to be 3.0 and 4.1, respectively. Conclusions: The annual mean analytical performance of Variant II Turbo HbA1c analyzer was found to be acceptable according to sigma metrics. In order to be sure of the difference in HbA1c results indicating the success or failure in treatment but not arise from analytical variation, it is thought that more stringent quality control measures should be applied to reach higher sigma levels.

scholarly journals Reproducibility and Instruction Following in the Shop Floor Laboratory Work: The Case of a TMS Experiment

2021 ◽  
pp. 016224392110323
Author(s):  
Kristina Popova
Keyword(s):  
Measurement Procedure ◽  
Shop Floor ◽  
Experimental Uncertainty ◽  
Local Measurement ◽  
Replication Crisis ◽  
History Of ◽  
Per Se ◽  
The Difference ◽  
Methodological Guidelines ◽  
Local Procedure

The article addresses the production of reproducibility as a topic that has become acutely relevant in the recent discussions on the replication crisis in science. It brings the ethnomethodological stance on reproducibility into the discussions, claiming that reproducibility is necessarily produced locally, on the shop floor, with methodological guidelines serving as references to already established practices rather than their origins. The article refers to this argument empirically, analyzing how a group of novice neuroscientists performs a series of measurements in a transcranial magnetic stimulation experiment. Based on ethnography and video analysis, the article traces a history of the local measurement procedure invented by the researchers in order to overcome the experimental uncertainty. The article aims to demonstrate (1) how reproducibility of the local procedure is achieved in the shop floor work of the practitioners and (2) how the procedure becomes normalized and questioned as incorrect in the course of experimental practice. It concludes that the difference between guidelines and practical actions is not problematic per se; what may be problematic is that researchers can be engaged in different working projects described by the same instruction.

scholarly journals Documenting metrological traceability as intended by ISO 15189:2012: A consensus statement about the practice of the implementation and auditing of this norm element

2019 ◽  
Vol 57 (4) ◽  
pp. 459-464 ◽  
Author(s):  
Marc Thelen ◽  
Florent Vanstapel ◽  
Pika Meško Brguljan ◽  
Bernard Gouget ◽  
Guilaine Boursier ◽  
...  
Keyword(s):  
Metrological Traceability ◽  
Measurement Procedure ◽  
Medical Laboratory ◽  
Clinical Samples ◽  
End User ◽  
Worst Case ◽  
Iso 15189 ◽  
Value Assignment ◽  
Traceability Chain ◽  
Medical Laboratories

Abstract ISO15189:2012 requires medical laboratories to document metrological traceability of their results. While the ISO17511:2003 standard on metrological traceability in laboratory medicine requires the use of the highest available level in the traceability chain, it recognizes that for many measurands there is no reference above the manufacturer’s selected measurement procedure and the manufacturer’s working calibrator. Some immunoassays, although they intend to measure the same quantity and may even refer to the same reference material, unfortunately produce different results because of differences in analytical selectivity as manufacturers select different epitopes and antibodies for the same analyte. In other cases, the cause is the use of reference materials, which are not commutable. The uncertainty associated with the result is another important aspect in metrological traceability implementation. As the measurement uncertainty on the clinical samples is influenced by the uncertainty of all steps higher in the traceability chain, laboratories should be provided with adequate and appropriate information on the uncertainty of the value assignment to the commercial calibrators that they use. Although the between-lot variation in value assignment will manifest itself as part of the long-term imprecision as estimated by the end-user, information on worst-case to be expected lot-lot variation has to be communicated to the end-user by the IVD provider. When laboratories use ancillary equipment that potentially could have a critical contribution to the reported results, such equipment needs verification of its proper calibration and criticality to the result uncertainty could be assessed by an approach based on risk analysis, which is a key element of ISO15189:2012 anyway. This paper discusses how the requirement for metrological traceability as stated in ISO15189 should be met by the medical laboratory and how this should be assessed by accreditation bodies.

Establishing an Accuracy Basis for the Vitamin D External Quality Assessment Scheme (DEQAS)

2017 ◽  
Vol 100 (5) ◽  
pp. 1277-1287 ◽  
Author(s):  
Carolyn Q Burdette ◽  
Johanna E Camara ◽  
Federica Nalin ◽  
Jeanita Pritchett ◽  
Lane C Sander ◽  
...  
Keyword(s):  
Vitamin D ◽  
Quality Assessment ◽  
External Quality Assessment ◽  
Measurement Procedure ◽  
Binding Assays ◽  
External Quality ◽  
External Quality Assessment Scheme ◽  
Hydroxyvitamin D ◽  
Target Values ◽  
High Concentrations

Abstract Until recently, the Vitamin D External Quality Assessment Scheme (DEQAS) assessed the performance of various assays for the determination of serum total 25-hydroxyvitamin D [25(OH)D] by using a consensus mean based on the all-laboratory trimmed mean (ALTM) of the approximately 1000 participants' results. Since October 2012, the National Institute of Standardsand Technology (NIST), as part of the Vitamin D Standardization Program, has participated in DEQAS by analyzing the quarterly serum sample sets using an isotope dilution LC-tandem MS (ID LC-MS/MS) reference measurement procedure to assign an accuracy-based target value for serum total 25(OH)D. NIST has analyzed90 DEQAS samples (18 exercises × 5 samples/exercise) to assign target values. The NIST-assigned values are compared with the ALTM and the biases assessed for various assays used by the participants, e.g., LC-MS/MS, HPLC, and several ligand-binding assays. The NIST-value assignment process and the resultsof the analyses of the 90 DEQAS samples are summarized. The absolute mean bias between the NIST-assignedvalues and the ALTM was 5.6%, with 10% of the samples having biases >10%. Benefits of the accuracy-based target values are presented, including for sample sets with high concentrations of 25(OH)D2 and 3-epi-25(OH)D3.

Performance Characteristics of Several Rules for Self-interpretation of Proficiency Testing Data

2005 ◽  
Vol 129 (8) ◽  
pp. 997-1003 ◽  
Author(s):  
R. Neill Carey ◽  
George S. Cembrowski ◽  
Carl C. Garber ◽  
Zohreh Zaki
Keyword(s):  
Proficiency Testing ◽  
Error Detection ◽  
Clinical Laboratory ◽  
Peer Group ◽  
Simulation Techniques ◽  
Allowable Error ◽  
Detection Capabilities ◽  
The Mean ◽  
The Difference

Abstract Context.—Proficiency testing (PT) participants can interpret their results to detect errors even when their performance is acceptable according to the limits set by the PT provider. Objective.—To determine which rules for interpreting PT data provide optimal performance for PT with 5 samples per event. Design.—We used Monte Carlo computer simulation techniques to study the performance of several rules, relating their error detection capabilities to (1) the analytic quality of the method, (2) the probability of failing PT, and (3) the ratio of the peer group SD to the mean intralaboratory SD. Analytic quality is indicated by the ratio of the PT allowable error to the intralaboratory SD. Failure of PT was defined (Clinical Laboratory Improvement Amendments of 1988) as an event when 2 or more results out of 5 exceeded acceptable limits. We investigated rules with limits based on the SD index, the mean SD index, and percentages of allowable error. Results.—No single rule performs optimally across the range of method quality. Conclusions.—We recommend further investigation when PT data cause rejection by any of the following 3 rules: any result exceeds 75% of allowable error, the difference between any 2 results exceeds 4 times the peer group SD, or the mean SD index of all 5 results exceeds 1.5. As method quality increases from marginal to high, false rejections range from 16% to nearly zero, and the probability of detecting a shift equal to 2 times the intralaboratory SD ranges from 94% to 69%.

Effects of lyophilization of serum on the measurement of apolipoproteins A-I and B

1990 ◽  
Vol 36 (2) ◽  
pp. 366-369 ◽  
Author(s):  
S M Marcovina ◽  
J L Adolphson ◽  
M Parlavecchia ◽  
J J Albers
Keyword(s):  
Reference Materials ◽  
Apolipoprotein B ◽  
Matrix Effects ◽  
Reference Intervals ◽  
Assay Method ◽  
Common Reference ◽  
Apolipoprotein A ◽  
Quality Control Materials ◽  
Standardization Process ◽  
The Difference

Abstract A common accuracy-based standardization program is indispensable for establishing reference intervals for the clinical use of apolipoproteins. The development and distribution of reference materials and quality-control materials that do not exhibit matrix effects between methods is essential to the standardization process. We examined the suitability of lyophilized material as a common reference material for the measurement of apolipoproteins A-I and B. We determined values for apolipoproteins A-I and B in frozen and lyophilized serum pools, using different immunochemical approaches. We found little or no differences in apolipoprotein A-I values between frozen and lyophilized pools as determined by the different methods. In contrast, values for apolipoprotein B in lyophilized samples were consistently lower than those obtained for frozen samples. After adjusting for the effect of dilution due to reconstitution, the difference in the apolipoprotein B values for lyophilized as compared with frozen samples ranged from -26% to 4%, depending upon the assay method. Evidently, serum pools in lyophilized from are not a suitable matrix for reference materials for apolipoprotein B measurements but can be used for apolipoprotein A-I measurements.

scholarly journals Bioluminescence-Based Neuraminidase Inhibition Assay for Monitoring Influenza Virus Drug Susceptibility in Clinical Specimens

2013 ◽  
Vol 57 (11) ◽  
pp. 5209-5215 ◽  
Author(s):  
Henju Marjuki ◽  
Vasiliy P. Mishin ◽  
Katrina Sleeman ◽  
Margaret Okomo-Adhiambo ◽  
Tiffany G. Sheu ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Point Of Care ◽  
Drug Susceptibility ◽  
Influenza Viruses ◽  
Clinical Specimens ◽  
Influenza Virus A ◽  
Oseltamivir Resistance ◽  
Resistance Markers ◽  
The Difference ◽  
Inhibitor Resistance

ABSTRACTThe QFlu prototype bioluminescence-based neuraminidase (NA) inhibition (NI) assay kit was designed to detect NA inhibitor (NAI)-resistant influenza viruses at point of care. Here, we evaluated its suitability for drug susceptibility assessment at a surveillance laboratory. A comprehensive panel of reference viruses (n= 14) and a set of 90 seasonal influenza virus A and B isolates were included for testing with oseltamivir and/or zanamivir in the QFlu assay using the manufacturer-recommended protocol and a modified version attuned to surveillance requirements. The 50% inhibitory concentrations (IC50s) generated were compared with those of NI assays currently used for monitoring influenza drug susceptibility, the fluorescent (FL) and chemiluminescent (CL) assays. To provide proof of principle, clinical specimens (n= 235) confirmed by real-time reverse transcription (RT)-PCR to contain influenza virus A(H1N1)pdm09 and prescreened for the oseltamivir resistance marker H275Y using pyrosequencing were subsequently tested in the QFlu assay. All three NI assays were able to discriminate the reference NA variants and their matching wild-type viruses based on the difference in their IC50s. Unless the antigenic types were first identified, certain NA variants (e.g., H3N2 with E119V) could be detected among seasonal viruses using the FL assays only. Notably, the QFlu assay identified oseltamivir-resistant A(H1N1)pdm09 viruses carrying the H275Y marker directly in clinical specimens, which is not feasible with the other two phenotypic assays, which required prior virus culturing in cells. Furthermore, The QFlu assay allows detection of the influenza virus A and B isolates carrying established and potential NA inhibitor resistance markers and may become a useful tool for monitoring drug resistance in clinical specimens.

Effect of Thickness Measurement Procedure on Stress Analysis of Pipes With Local Metal Loss

2013 ◽  
Author(s):  
Nobuyuki Yoshida ◽  
Atsushi Yamaguchi
Keyword(s):  
Decision Making ◽  
Measurement Procedure ◽  
Thickness Measurement ◽  
Burst Pressure ◽  
Metal Loss ◽  
Element Analysis ◽  
Fea Model ◽  
Laser Displacement Meter ◽  
The Difference ◽  
Corrosion Under Insulation

Fitness-For-Service (FFS) assessment using Finite Element Analysis (FEA) has been a problem in deciding yes-no which vary from evaluator to evaluator. The difference in decision making is caused by the degree of freedom in modeling a FEA model. In this study, burst pressures of pipes with local metal loss were calculated by using FEA in order to investigate the influence of thickness measurement intervals on FFS assessment. The analyzed pressures by FEA were verified by burst tests. A pipe specimen, which was thinned by corrosion under insulation in the actual plant, was used for the burst tests. Shape of the pipe specimen was measured by laser displacement meter and extracted at several types of interval. It is concluded that the analyzed pressures in various measurement intervals showed almost no difference, but were higher than the actual burst pressure of the specimen.

Intra- and interlaboratory sources of imprecision in drug measurements by different techniques

1993 ◽  
Vol 39 (5) ◽  
pp. 851-855 ◽  
Author(s):  
L M Tsanaclis ◽  
J F Wilson
Keyword(s):  
External Quality Assessment ◽  
Serum Samples ◽  
External Quality Assessment Scheme ◽  
Drug Concentrations ◽  
Bartlett’S Test ◽  
Homogeneity Of Variance ◽  
Sources Of Variation ◽  
Laboratory Procedures ◽  
Assay Precision ◽  
Using Data

Abstract We compared the intra- and interlaboratory precision of seven techniques used to measure eight antiepileptic drugs, digoxin, and theophylline by using data from the international Healthcontrol external quality-assessment scheme. Scheme participants were supplied blind with 6 or 12 sets of duplicate lyophilized serum samples. Each set contained different drug concentrations, and duplicates were analyzed separately, 1 to 6 months apart. The intra- and interlaboratory components of assay variance were isolated and compared by Bartlett's test for homogeneity of variance. Fluorescence polarization immunoassay (Abbott) showed the best overall intra- and interlaboratory performance for a range of analytes. The largest intralaboratory errors were produced by techniques using the Syva EMIT assays. Our analysis of the data shows that for most analyte/technique combinations, intralaboratory sources of variation were more important than interlaboratory sources. Gains in assay precision will therefore result from attention to internal laboratory procedures.

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