External Quality Assessment Materials Research Articles

PB1039 Evaluation of External Quality Assessment Material for Activated Clotting Time on Point of Care Devices: United Kingdom National External Quality Assessment Scheme for Blood Coagulation Pilot Studies

PB1039 Evaluation of External Quality Assessment Material for Activated Clotting Time on Point of Care Devices: United Kingdom National External Quality Assessment Scheme for Blood Coagulation Pilot Studies

PB1041 Evaluation of External Quality Assessment Material on the Renovated Point of Care Device, United Kingdom National External Quality Assessment Scheme for Blood Coagulation Studies

PB1041 Evaluation of External Quality Assessment Material on the Renovated Point of Care Device, United Kingdom National External Quality Assessment Scheme for Blood Coagulation Studies

Recommendations for Setting a Criterion and Assessing Commutability of Sample Materials Used in External Quality Assessment/Proficiency Testing Schemes.

It is important for external quality assessment materials (EQAMs) to be commutable with clinical samples; i.e., they should behave like clinical samples when measured using end-user clinical laboratory in vitro diagnostic medical devices (IVD-MDs). Using commutable EQAMs makes it possible to evaluate metrological traceability and/or equivalence of results between IVD-MDs. The criterion for assessing commutability of an EQAM between 2 IVD-MDs is that its result should be within the prediction interval limits based on the statistical distribution of the clinical sample results from the 2 IVD-MDs being compared. The width of the prediction interval is, among other things, dependent on the analytical performance characteristics of the IVD-MDs. A presupposition for using this criterion is that the differences in nonselectivity between the 2 IVD-MDs being compared are acceptable. An acceptable difference in nonselectivity should be small relative to the analytical performance specifications used in the external quality assessment scheme. The acceptable difference in nonselectivity is used to modify the prediction interval criterion for commutability assessment. The present report provides recommendations on how to establish a criterion for acceptable commutability for EQAMS, establish the difference in nonselectivity that can be accepted between IVD-MDs, and perform a commutability assessment. The report also contains examples for performing a commutability assessment of EQAMs.

Commutability assessment of candidate reference materials for plasma renin activity measurement: current challenges.

This study aims to evaluate the commutability of external quality assessment (EQA) materials and candidate reference materials (RMs) for plasma renin activity (PRA) assay. Commutabilities of 16 candidate RMs were measured along with 40 clinical samples by the four different routine PRA assays, including three LC‒MS/MS assays and onechemiluminescence immunoassay. Sixteen candidate RMs included native/spiked human plasma pools (small-scale pools with <50 individuals) and current EQA materials (large-scale pools with >1,000 individuals). Difference inbias approach and linear regression with prediction interval approach were adopted to determine the commutability. Two-way variance analysis was used to estimate the effects of spiked and pool size on the commutability. Stability and homogeneity studies were performed. Precision and correlation performance of all assays was acceptable. In the difference in bias approach, thecommutability results were not satisfactory (noncommutability: 14/16) and significant sample-specific effects were detected in assay pairs using different incubation buffers. For the prediction interval approach, no commutability was observed in the spiked small-scale pools; EQA materials (4/9) had more satisfactory commutability among all assays than the small-scale pools (2/7); RMs of large-scale pools tend to have better commutability no matter spiked ornot. Commutable RMs were obtainable but challenging. Current EQA materials with relatively good commutability, stability, and homogeneity were appropriate RMs. Large-scale pools are tending to be commutable. Spiking in small-scale pools was not suggested to prepare RMs. MPs adopting a uniform incubation buffer would be preferable for further commutability research.

Aggregated data from the same laboratories participating in two glucose external quality assessment schemes show that commutability and transfers of values to control materials are decisive for the biases found.

We report the results of glucose measurements performed during one year by the same measurement procedures (MPs) in 58 Norwegian hospital laboratories using control materials provided by external quality assessment (EQA) schemes from two different providers. The providers used materials with presumed vs. verified commutability and transfers of values using reference material vs. using a highest-order reference MP. Data from six Labquality and three Noklus glucose EQA surveys were aggregated for each MP (Abbott Alinity, Abbott Architect, Roche Cobas, and Siemens Advia) in each scheme. For each EQA result, percent difference from target value (% bias) was calculated. Median percent bias for each MP per scheme was then calculated. The median % biases observed for each MP in the Labquality scheme were significantly larger than those in the Noklus scheme, which uses verified commutable control materials and highest-order reference MP target values. The difference ranged from 1.2 (Roche Cobas, 2.9 vs. 1.7 %) to 4.4 percentage points (Siemens Advia, 3.2 % vs.-1.2 %). The order of bias size for the various MPs was different in the two schemes. In contrast to the Labquality scheme, the median % biases observed in the Noklus scheme for Abbott Alinity (-0.1 %), Abbott Architect (-0.5 %), and Siemens Advia (-1.2 %) were not significantly different from target value (p>0.756). This study underlines the importance of using verified commutable EQA materials and target values traceable to reference MPs in EQA schemes designed for assessment of metrological traceability of laboratory results.

Exploration of suitable external quality assessment materials for serum C-peptide measurement.

To find suitable external quality assessment (EQA) materials for serum C-peptide, we evaluated the commutability of five types of processed materials. Seventy-four individual serum samples and 12 processed samples including three EQA samples currently in use, frozen human serum pools (FHSP), and three other kinds of processed samples were prepared by dissolving WHO International Standard Reagent for C-peptide (WHO ISR 13/146) in three different matrixes: 0.05 % bovine serum albumin, fetal bovine serum and human serum pools. Samples were analyzed using the isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method and six widely used immunoassays. The commutabilities of processed materials were assessed according to the difference in bias approach recommended by the IFCC. And the short- and long-term stability of FHSP samples at different temperatures were also evaluated. Out of the five kinds of processed materials, FHSP samples were commutable on most assays. In contrast, the EQA materials currently in use were only commutable on a few immunoassays. Additionally, processed materials derived from WHO ISR 13/146 were found to be un-commutable on over half of immunoassays. The FHSP samples could be stably stored at 4 and-20 °C for at least 16days, and at-80 °C for at least 1 year, but at room temperature only for 12 h. With clarified commutability and stability information, the human serum pool samples along with the developed ID-LC-MS/MS method could be used in the EQA program to promote the comparability among laboratories for C-peptide measurement in China.

External quality assessment practices in medical laboratories: an IFCC global survey of member societies.

Clinical laboratory results are required for critical medical decisions, underscoring the importance of quality results. As part of total quality management, external quality assessment (EQA) is a vital component to ensure laboratory accuracy. The goal of this survey was to evaluate the current status of global laboratory quality systems and assess the need for implementation, expansion, or harmonization of EQA programs (EQAP) for Clinical Chemistry and Laboratory Medicine. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Task Force on Global Laboratory Quality (TF-GLQ) conducted a survey of IFCC full and affiliate members (n=110) on laboratory quality practice. A total of 41 (37.3%) countries representing all IFCC regions except North America provided responses about EQA availability and practices. All 41 countries perform EQA, 38 reported that their laboratories had EQA policies and procedures, and 39 further act/evaluate unacceptable EQA results. 39 countries indicated they have international and/or national EQAP and 30 use alternative performance assessments. EQA frequency varied among countries. Generally, an EQAP provided the EQA materials (40/41) with four countries indicating that they did not have an EQAP in their country. Globally, most laboratories participate in an EQAP and have defined quality procedures for EQA. There remain gaps in EQA material availability and implementation of EQA as a part of a total laboratory quality system. This survey highlights the need for education, training, and harmonization and will guide efforts of the IFCC TF-GLQ in identifying areas for enhancing global laboratory quality practices.

Establishment of External Quality Assessment Material Preparation Method for Next-Generation Sequencing-Based Liquid Biopsy Scheme

Establishment of External Quality Assessment Material Preparation Method for Next-Generation Sequencing-Based Liquid Biopsy Scheme

UK NEQAS Haematology pilot scheme: Reticulocyte haemoglobin content quantitation.

Established parameters for the investigation of suspected iron deficiency have recognized limitations that affect their sensitivity and specificity. Reticulocyte haemoglobin content (RHC) is an early biomarker of iron deficiency or restriction, which also demonstrates response to iron therapy. RHC parameters are offered on all major automated haematology analysers. There is no external quality assessment (EQA) for RHC in the UK, restricting its wider clinical application. The UK National External Quality Assessment Scheme (UKNEQAS) for Haematology has completed a pilot study on the use of stabilized blood for RHC EQA. Blood was obtained from two JAK2 V617F mutation-positive, polycythaemia vera patients undergoing regular venesection, and from a healthy volunteer donor. Aliquots of each donation were distributed to users of Abbott, Horiba, Siemens and Sysmex automated analysers for RHC analysis on days 1, 3, 5 and 7. Results were received from 20 laboratories using four different platforms. The daily mean and standard deviation (SD) were calculated for each aliquot, by day of analysis and platform. With RHC there was no significant within-platform difference (p> 0.5) between testing days, although there were statistically significant differences (p< 0.001) between different platforms. The greatest difference was seen between Abbott MCHr and Horiba RhCc (-6.14 ± 1.25 pg). Despite inter-platform differences, it was possible to define iron deficient, borderline, and normal cut-offs to classify 95% of results correctly. The results demonstrate that it is possible to provide RHC EQA material using UKNEQAS standard procedures. The results are clinically relevant but indicate a requirement for inter-user comparison.

Commutability Assessment of Processed Human Plasma Samples for Normetanephrine and Metanephrine Measurements Based on the Candidate Reference Measurement Procedure.

BackgroundTo identify candidate external quality assessment (EQA) materials for normetanephrine and metanephrine measurements, we assessed the commutability of eight processed human plasma samples. The agreement between routine assays and the candidate reference measurement procedure (cRMP) was also evaluated.MethodsFifty-three clinical samples and eight processed plasma samples were prepared. The processed samples included pooled and individual plasma samples spiked with pure normetanephrine and metanephrine and non-spiked pooled and individual plasma samples. The clinical and processed samples were subjected to four routine isotope dilution tandem mass spectrometry assays and cRMP. Commutability was assessed based on two approaches recommended by the CLSI and International Federation of Clinical Chemistry (IFCC). Passing–Bablok regression and Bland–Altman analysis were used to evaluate the agreement between the routine assays and cRMP.ResultsThe commutability results of the CLSI approach were better than those of the IFCC approach. For the CLSI approach, spiked individual plasma samples and spiked high-concentration pooled plasma samples were commutable for all routine assays for both analytes. The non-spiked pooled plasma sample was commutable for two out of four routine assays for metanephrine and three out of four routine assays for normetanephrine. The agreement between the routine assays and the cRMP was satisfactory, except for one routine assay showing significant bias.ConclusionsHigh-concentration spiked pooled plasma samples and spiked individual plasma samples are candidate EQA materials for normetanephrine and metanephrine measurements.

External quality assessment for detection of methylated Syndecan 2 (SDC2) in China.

Detection of Syndecan 2 (SDC2) methylation in stool DNA is a novel method for the auxiliary diagnosis of early colorectal cancer (CRC). Currently, this method has been widely applied; however, its accuracy and reliability have not been determined. The objective of this pioneering study was to evaluate the performance of clinical laboratories in China for their ability to detect SDC2 methylation from stool DNA. We generated a sample panel consisting of clinical and cell samples. The clinical samples were stool specimens from patients with or without CRC, including four positives (prepared by serial dilution from one stool specimen), one negative and one interferential sample. Two cell samples, with positive or negative methylated SDC2, were used as controls. The panel was distributed to 32 clinical laboratories for analysis of SDC2 methylation, and the results were compared and scored. The sample panel was compatible with commercially available assays and it showed appropriate stability to be an external quality assessment material. There were four false results; one hospital laboratory and one commercial diagnostic laboratory had a false-positive and a false-negative result, respectively, and one commercial diagnostic laboratory had both a false-positive and false-negative result. Among the 32 participating laboratories, 29 (90.62%) obtained an acceptable or better performance score, while 3 (9.38%) laboratories required improvement. Our results demonstrate that the detection of SDC2 methylation from stool DNA was satisfactory in China. Additionally, the importance of external quality assessment was highlighted for monitoring the performance of clinical laboratories.

M222 Evaluation of commutability of external quality assessment material for accuracy based survey of lipid tests

M222 Evaluation of commutability of external quality assessment material for accuracy based survey of lipid tests

Formation and Evaluation of Complete Blood Count Proficiency Testing Program.

Introduction: The haematology external quality assessment (EQA) scheme is the most commonly used service of quality assurance. The provision of complete blood count (CBC) materials must meet the quality requirements at a reasonable cost. These requirements are the most significant challenges for EQA organisers in Vietnam. This study’s objective was to evaluate the homogeneity, long-term stability, and peer-group performance of 10-parameter stabilised CBC EQA samples. Methods: The CBC EQA material was prepared using the following steps, including (1) adjusting levels of stabilised erythrocyte, leukocyte, and platelet samples, (2) mixing those cells into batches at three levels, and (3) dispensing and storing them at 2–6 °C. A set of 10 and 30 specimens were randomly chosen from each batch to study the homogeneity and long-term stability following ISO 13528:2015. In total, 166 samples at two levels were randomly distributed to 40 participants, which reported 83 automatic cell counters among six automated analyser models in the CBC EQA program. Results: The 10-parameter stabilised CBC EQA materials at three levels became homogeneous and stable in 12 weeks when preserved at 2–6 °C. Meanwhile, for five parameters (RBC, Hb, MCH, MCV, and MPV), this process was prolonged for up to 16 weeks in stock condition. In terms of peer-group performance, the CV (%) values increased at the low concentration for almost all parameters, especially in platelet counts. Conclusions: The stabilised CBC EQA samples prepared using the partial fixation method with aldehyde and gutaraldehyde in this study meet the ISO 13528:2015 requirements of homogeneity and long-term stability for the CBC EQA scheme. Analytical performance evaluation should categorise participant methods into peer groups.

Report from the HarmoSter study: impact of calibration on comparability of LC-MS/MS measurement of circulating cortisol, 17OH-progesterone and aldosterone.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is recommended for measuring circulating steroids. However, assays display technical heterogeneity. So far, reproducibility of corticosteroid LC-MS/MS measurements has received scant attention. The aim of the study was to compare LC-MS/MS measurements of cortisol, 17OH-progesterone and aldosterone from nine European centers and assess performance according to external quality assessment (EQA) materials and calibration. Seventy-eight patient samples, EQA materials and two commercial calibration sets were measured twice by laboratory-specific procedures. Results were obtained by in-house (CAL1) and external calibrations (CAL2 and CAL3). We evaluated intra and inter-laboratory imprecision, correlation and agreement in patient samples, and trueness, bias and commutability in EQA materials. Using CAL1, intra-laboratory CVs ranged between 2.8-7.4%, 4.4-18.0% and 5.2-22.2%, for cortisol, 17OH-progesterone and aldosterone, respectively. Trueness and bias in EQA materials were mostly acceptable, however, inappropriate commutability and target value assignment were highlighted in some cases. CAL2 showed suboptimal accuracy. Median inter-laboratory CVs for cortisol, 17OH-progesterone and aldosterone were 4.9, 11.8 and 13.8% with CAL1 and 3.6, 10.3 and 8.6% with CAL3 (all p<0.001), respectively. Using CAL1, median bias vs. all laboratory-medians ranged from-6.6 to 6.9%,-17.2 to 7.8% and-12.0 to 16.8% for cortisol, 17OH-progesterone and aldosterone, respectively. Regression lines significantly deviated from the best fit for most laboratories. Using CAL3 improved cortisol and 17OH-progesterone between-method bias and correlation. Intra-laboratory imprecision and performance with EQA materials were variable. Inter-laboratory performance was mostly within specifications. Although residual variability persists, adopting common traceable calibrators and RMP-determined EQA materials is beneficial for standardization of LC-MS/MS steroid measurements.

Assessment of Minimal/Measurable Residual Disease Testing in Acute Myeloid Leukaemia By Molecular Methods in an Interlaboratory Study

BackgroundMinimal/measurable residual disease (MRD) testing is increasingly utilised and accepted as standard of care to manage a range of different haematological malignancies. It's use as a surrogate outcome in clinical trials of new therapies is being explored, where it has the potential to accelerate drug assessment and approval. The phenotypic and genetic heterogeneity of acute myeloid leukaemia (AML) has limited the use of MRD in this context; however, the European LeukaemiaNet (ELN) MRD working group have recently published consensus guidelines to standardise both flow cytometric and molecular genetic MRD testing. To assess the accuracy of testing and concordance between laboratories, crucial to patient safety, external quality assessment (EQA)/proficiency testing (PT) is required.AimsTo determine the performance of molecular methods for measuring of MRD using the t(8;21)(q22:q22) RUNX1-RUNX1T1, inv(16)(p13q22) CBFB-MYH11, t(15;17)(q24.1;q21.2) PML-RARA and NPM1 Type A markers in an international interlaboratory study.MethodsA total of 12 batches of lyophilised EQA material were manufactured. These consisted of three batches of samples for each marker all containing 9x10^6 cells: an MRD ‘high’ sample; an MRD ‘low’ sample; and an MRD ‘negative’ sample. The t(8;21)(q22:q22) RUNX1-RUNX1T1 positive samples were manufactured using the KASUMI-1 cell line, the inv(16)(p13q22) CBFB-MYH11 positive samples using the ME-1 cell line; t(15;17)(q24.1;q21.2 PML-RARA positive samples using the NB4 cell line and the NPM1 Type A (NM_002520.6:c.860_863dup) positive samples using the OCI-AML3 cell line. MRD positive samples were diluted with HL60 cells to achieve the desired MRD level. MRD negative samples were manufactured using the HL60 cell line. The samples were shipped at ambient temperature to the 29 laboratories in 12 countries. Participants were asked to test the blinded samples with their in-house assay and report % normalised ratio of the relevant marker alongside additional methodological and technical data.ResultsFor t(8;21) RUNX1-RUNX1T1, all participants who returned results (n=23) classified the MRD ‘high’ and MRD ‘low’ samples as positive and the MRD ‘negative’ sample as negative. The robust mean log reduction between the MRD ‘high’ and MRD low sample was 2.7 (range 2.5-2.9). For inv(16) CBFB-MYH11, all participants who returned results (n=22) classified the MRD ‘high’ sample as positive, 21/22 (95.5%) classified the MRD ‘low’ sample as positive and 21/22 (95.5%) classified the MRD negative sample as negative. The robust mean log reduction between the MRD ‘high’ and MRD ‘low’ sample was 3.16 (range 2.8-4.2). For t(15;17) PML-RARA, all participants who returned results (n=22) classified the MRD ‘high’ sample as positive, 21/22 (95.5%) classified the MRD ‘low’ sample as positive and 21/22 (95.5%) classified the MRD negative sample as negative. The robust mean log reduction between the MRD ‘high’ and MRD ‘low’ sample was 2.1 (range 1.4-2.4). For NPM1, all participants who returned results (n=23) classified the MRD ‘high’ as positive, 21/23 (91.3%) classified the MRD ‘low’ sample as positive and, 17/23 (73.4%) classified the MRD negative sample as negative. The robust mean log reduction between the MRD ‘high’ and MRD ‘low’ sample was 3.8 (range 3.2-4.2).Summary/ConclusionThe majority of participants in this study were able to detect and accurately quantify MRD when assessing the t(8;21)(q22:q22) RUNX1-RUNX1T1, inv(16)(p13q22) CBFB-MYH11, t(15;17)(q24.1;q21.2) PML-RARA and NPM1 markers, at levels that would be expected within a clinical trial or standard of care setting. A high proportion of participants reported false positive results in the NPM1 marker negative sample. This would have significant consequences clinically, with NPM1 marker false-positivity potentially committing patients to unneeded additional chemotherapy and/or transplant with the attendant risk of morbidity and mortality which highlights the need for ongoing EQA in this area. UK NEQAS LI will work with laboratories advocating they undertake a root cause analysis process to identify the source(s) of error contributing to false positive NPM1 marker results and support their subsequent corrective actions; sharing any educational findings with all participants. [Display omitted] DisclosuresScott: Novartis: Research Funding; Biorad: Research Funding. Dillon: Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Research Support, Educational Events; Amgen: Other: Research support (paid to institution); Astellas: Consultancy, Other: Educational Events , Speakers Bureau; Menarini: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Session chair (paid to institution), Speakers Bureau; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: educational events; Jazz: Other: Education events; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees. Whitby: Roche: Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Other: Teaching.

Development of a Method for Manufacturing External Quality Assessment Material for Genetic Testing of Solid Tumors Using Mutant and Wild-Type Cell Lines

Development of a Method for Manufacturing External Quality Assessment Material for Genetic Testing of Solid Tumors Using Mutant and Wild-Type Cell Lines

Evaluation of the necessity and the feasibility of the standardization of procalcitonin measurements: Activities of IFCC WG-PCT with involvement of all stakeholders

Procalcitonin (PCT) is an important biomarker for sepsis diagnosis and management. To date, there is no higher-order reference measurement procedure (RMP) and certified reference material to achieve global standardization of results and results traceability to the SI units. Although efforts have been made to harmonize PCT results, a number of comparison studies and external quality assessment (EQA) schemes show conflicting results regarding results comparability and to date, equivalence of PCT results across the assays remains questionable in absence of studies relying on commutable EQA materials. In this context, the IFCC initiated activities to fill these gaps through the creation of the working group on standardization of PCT assays that gathers experts from National Metrology Institutes, calibration laboratories, clinicians, biologists, EQA providers and assay manufacturers. Among the activities, a higher order RMP and commutable reference materials are under development to build a robust reference measurement system (RMS). A commutability study is being organized to identify EQA materials that are fit for purpose to reliably estimate the current comparability of PCT results. This work will make it possible to evaluate the necessity and the feasibility for establishing and maintaining a new RMS for PCT assays, if deemed necessary.

Commutability Assessment of Candidate External Quality Assessment Materials for Aminotransferase Activity Measurements Based on Different Approaches in China.

BackgroundUsing commutable external quality assessment (EQA) materials is important for monitoring successful harmonization efforts. We assessed the commutability of four human serum pool (HSP) preparations to identify candidate EQA materials for alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity measurement.MethodsOne set each of 85 clinical samples (CSs) was collected for ALT and AST activity measurement. The 15 candidate EQA materials included four types of HSP preparations (A to D): materials A, C, and D contained human original recombinant (HOR) aminotransferases; materials B was mixed leftover samples. The CSs and 15 candidate EQA materials were analyzed using seven routine assays, and the ln-transformed results were analyzed in 21 assay pairs. Commutability was assessed using Deming regression, with a 95% prediction interval (CLSI approach) and the difference in bias with an error component model (International Federation of Clinical Chemistry and Laboratory Medicine [IFCC] approach).ResultsFor ALT, all materials were commutable for 14–21 assay pairs according to the CLSI and IFCC approaches. For AST, B01–03 showed commutability for 14–21 assay pairs, and C01–03 and D01–03 showed commutability for no less than 10 assay pairs according to the two approaches. A01–06 were commutable for 9–16 assay pairs according to the CLSI approach, but for 6–9 assay pairs according to the IFCC approach.ConclusionsMixed leftover samples showed desirable commutability characteristics as candidate EQA materials for routine aminotransferase activity measurements. Human serum bases supplemented with HOR were commutable for most routine ALT activity measurements.

Causes behind error rates for predictive biomarker testing: the utility of sending post-EQA surveys

External quality assessment (EQA) schemes assess the performance of predictive biomarker testing in lung and colorectal cancer and have previously demonstrated variable error rates. No information is currently available on the underlying causes of incorrect EQA results in the laboratories. Participants in EQA schemes by the European Society of Pathology between 2014 and 2018 for lung and colorectal cancer were contacted to complete a survey if they had at least one analysis error or test failure in the provided cases. Of the 791 surveys that were sent, 325 were completed including data from 185 unique laboratories on 514 incorrectly analyzed or failed cases. For the digital cases and immunohistochemistry, the majority of errors were interpretation-related. For fluorescence in situ hybridization, problems with the EQA materials were reported frequently. For variant analysis, the causes were mainly methodological for lung cancer but variable for colorectal cancer. Post-analytical (clerical and interpretation) errors were more likely detected after release of the EQA results compared to pre-analytical and analytical issues. Accredited laboratories encountered fewer reagent problems and more often responded to the survey. A recent change in test methodology resulted in method-related problems. Testing more samples annually introduced personnel errors and lead to a lower performance in future schemes. Participation to quality improvement projects is important to reduce deviating test results in laboratories, as the different error causes differently affect the test performance. EQA providers could benefit from requesting root cause analyses behind errors to offer even more tailored feedback, subschemes, and cases.

Commutability of possible external quality assessment materials for progesterone measurement

BackgroundThe commutability of control materials used for external quality assessment (EQA) programs is of great importance. Evaluating the commutability of control materials is crucial to assess their suitability for EQA programs. MethodsForty-eight individual patient serum samples, commercial EQA samples, human serum pools (HSPs), commercially available sterile filtered charcoal stripped serum (CS) and swine serum were analyzed using the isotope dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) comparative method and six immunoassays for progesterone. The commutability was assessed according to the EP14-A2 guideline and the difference in bias approach, respectively. ResultsAccording to the EP14-A2 guideline, HSPs and CS were commutable for all the tested immunoassays, while swine serum showed positive matrix effects in some assays. Based on the difference in bias approach, a large number of inconclusive and noncommutable results appeared. ConclusionsThe commutability of the processed materials varied depending on which evaluation approach and criterion was applied. Noncommutability of the EQA materials was observed. And HSPs and CS were possible commutable candidate control materials according to the EP14-A2 guideline.