External Quality Assessment Scheme Research Articles

Comparison of fecal calprotectin and pancreatic elastase assays based on proficiency testing results

BackgroundFecal calprotectin and fecal pancreatic elastase assays are not standardized because of a lack of suitable reference material. Laboratories may have difficulty in switching assays because different manufacturers do not compare well with each other despite having similar reference intervals. Data from proficiency testing performed in Germany (Fecal Diagnostics 01 Survey, INSTAND eV) were investigated to understand how results differed across eight calprotectin and five pancreatic elastase manufacturers. MethodsData were collected from participating laboratories in external quality assessment schemes from 2015 to 2020 for calprotectin and 2017 to 2020 for pancreatic elastase. The manufacturer group mean values and standard deviations were calculated. Reference points were created for each external quality assessment scheme by calculating the average of all manufacturer group means. Deming regression analyses were used to observe the differences across manufacturers. ResultsThe slopes of the Deming regression spanned 0.37–1.91 for calprotectin and 0.84–1.33 for pancreatic elastase. The calprotectin assays had a high degree of variability in quantitative results by manufacturer. However, pancreatic elastase assays appear to be harmonized across the different manufacturer when considering the qualitative interpretation. ConclusionsBoth calprotectin and pancreatic elastase assays could be improved by standardization efforts. Given the clinical utility and our data demonstrating high inter-manufacturer variability, calprotectin should be prioritized over pancreatic elastase in standardization efforts.

Blended Bilingual Education Model in Chinese-Foreign Cooperatively-Run Programs in Higher Vocational Colleges With Foreign Language Other Than English as the Target Language

Bilingual teaching modules are commonly seen in Chinese-foreign cooperatively-run classes with English as the foreign language. In Chinese-foreign cooperatively-run classes with foreign languages other than English, blended bilingual education model is suggested with different bilingual education models applied in different courses and terms. This model may also face the challenges like comparatively high learning objectives and inefficient learners as well as limited bilingual teaching resources. To ensure its quality, both external and internal quality assurance schemes are suggested.

M226 New external quality assessment scheme for fecal occult blood in Thailand

M226 New external quality assessment scheme for fecal occult blood in Thailand

M233 Patient based real time quality control as a complementary tool to external quality assessment schemes in clinical laboratories

M233 Patient based real time quality control as a complementary tool to external quality assessment schemes in clinical laboratories

Epidemiology, Management, Quality of Testing and Cost of Syphilis in Germany: A Retrospective Model Analysis.

BackgroundA multi-dimensional model can be a useful tool for estimating the general impact of disease on the different sectors of the healthcare system. We chose the sexually transmitted disease syphilis for our model due to the good quality of reported data in Germany.MethodsThe model included gender- and age-stratified incident cases of syphilis (in- and outpatients) provided by a German statutory health insurance company, as well as seroprevalence data on syphilis in first-time blood donors. Age standardized rates were calculated based on the standard German population. The test quality was assessed by extrapolating the number of false-positive and false-negative results based on data from Europe-wide external quality assessment (EQA) schemes. The model analysis was validated with the reported cases and diagnosis-related group (DRG)-statistics from 2010 to 2012. The annual direct and indirect economic burden was estimated based on the outcomes of our model.ResultsThe standardized results were slightly higher than the results reported between 2010 and 2012. This could be due to an underassessment of cases in Germany or due to limitations of the dataset. The number of estimated inpatients was predicted with an accuracy of 89.8 %. Results from EQA schemes indicated an average sensitivity of 92.8 % and an average specificity of 99.9 % for the recommended sequential testing for syphilis. Based on our model, we estimated a total average minimal annual burden of €20,292,110 for syphilis on the German healthcare system between 2010 and 2012.ConclusionsThe linking of claims data, results from EQA schemes, and blood donor surveillance can be a useful tool for assessing the burden of disease on the healthcare system. It can help raise awareness in populations potentially at risk for infectious diseases, demonstrate the need to educate potential risk groups, and may help with predictive cost calculations and planning.

Characterization and traceability of two generations of standard reference material for the measurement of vitamin K1 (phylloquinone) at endogenous concentrations in human plasma and serum.

Vitamin K is an essential micronutrient required for blood coagulation, regulation of vascular calcification and bone mineralization. Plasma and serum measurements of vitamin K1 (phylloquinone, K1 ) made using high-performance liquid chromatography with fluorescence detection, or tandem mass spectrometry are used clinically and in population studies to assess vitamin K status. Standard reference materials provide a validation tool for laboratories, helping assure clinical diagnosis and the comparability of data from different populations. We manufactured two K1 standard reference materials, in 2009 (KEQAS SRM-001) and in 2019 (KEQAS SRM-002). The target concentrations of K1 were assigned to each SRM using the All Laboratory Trimmed Mean of results reported by selected laboratories enrolled in the Vitamin K External Quality Assurance Scheme (KEQAS). The assigned concentrations of K1 for KEQAS SRM-001 and SRM-002 were 0.25 and 0.36 μg/L respectively. In 2019 KEQAS SRM-001 was re-analysed simultaneously with KEQAS SRM-002 to provide traceability between the two standards, therefore aiding comparability of analysis performed using these materials. Both standards were stored as aliquots at -80°C in the dark; annual re-analysis of the materials indicated that K1 is stable for at least 12 years in these conditions.

Application of sigma metrics in haematology laboratory

Objectives: Sigma metrics analysis indicates; the level quality control has achieved and how far a given process deviates from perfection. Though the concept is not new to quality and utility, its implementation in the haematology laboratory is still in its nascent stages. The study aimed to compare the utility of sigma metrics as a comprehensive quality control tool in Haematology laboratory against the current quality tools of Internal Quality Control (IQC) and External quality assurance scheme for haematology analyser.Methods: In the present study, IQC data was analysed from June 2021 to September 2021. Control material included 3 batches of second party controls (SPC). Sigma were calculated for five key haematological parameters run in Sysmex XN 350. OPSpecs charts were prepared. Sigma metrics were calculated using the formula Sigma = (TEa – Bias) / CV, Bias was taken from IQC kit insert. Quality goal index was also calculated when needed.Results: Average sigma metrics achieved for selected parameters was, RBC: 8.1, HB: 7.6, HCT 5.6, PLT: 7.0, and WBC: 6.7. The laboratory has achieved excellent to world class performance in all analytes. Sigma QC rules were applied and modifications proposed to the existing internal QC protocols to reduce the number of rejections.Conclusion: Labs must preferentially use the sigma metrics and sigma QC rules to design its IQC protocols, for individual parameters, rather than follow the ‘one fit for all’ recommendation. This would help save precious time, effort, unnecessary control runs and improve efficiency with better focus on quality control, where required.

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.

The Process of Establishing and Managing a Laboratory Diagnostic Network in the COVID-19 Pandemic in Iran

The COVID-19 pandemic caused by the newly emerged coronavirus was first detected in China in December 2019 and rapidly spread worldwide. The rapid spread of the disease urged all countries involved, in accordance with their capacities, take the necessary measures to diagnose and manage the disease. The first patient was diagnosed with COVID-19 in Iran in February 2020. Considering the significant role of the laboratory services in detection and management of the disease, planning and programming to provide access to these services was considered as a top priority for healthcare system in Iran. Adopting all existing laboratory capacities and providing necessary infrastructures for expanding COVID-19 laboratory diagnostics, resulted in the establishment of a nationwide network of COVID-19 molecular diagnostic laboratories within the shortest possible time. In addition to expanding the capacity of laboratory services, improving the laboratory network’s performance have been taken into serious consideration. Despite the strict sanctions, the COVID-19 molecular diagnostic laboratories scaled up to more than 430 laboratories currently (September 2021), mostly are operating in the private sector. With considerable efforts, COVID-19 molecular laboratory network was established to provide nationwide diagnostic services. Considering the capacity for the SARS-CoV-2 Rapid Antigen test, we can now perform more than 100,000 COVID-19 diagnostic tests per day. However, due to the ongoing pandemic and in accordance with the requirements of the health system, it is necessary to plan and carry out more COVID-19 diagnostic tests. This study aimed to introduce the process of establishing the COVID-19 laboratory diagnostic network to manage the COVID-19 pandemic in Iran.

Determination of Sigma metric based on various TEa sources for CBC parameters: the need for Sigma metrics harmonization

Abstract Objectives The application of Sigma metrics can be used for assessing the performance of diagnostic laboratories. Clinical laboratories are confronted with the trouble of having to select the best and suitable quality specifications that are required for quality planning. In this regard, our study aims at evaluating the performance of Sysmex XN-1000 hematology analyzer by using Sigma metrics based on different total allowable error (TEa) source and to determine the effects of these variations in Sigma metric evaluation. Methods Five TEa requirements were selected to calculate Sigma metrics of 11 complete blood count (CBC) parameters. Coefficient of variation (CV) and bias data were supplied from internal quality control (IQC) and External Quality Assessment Scheme (EQAS) respectively. Results According to TEa based on desirable biological variation (BV) database specifications, the highest Sigma value was achieved by white blood cell count for each level, the lowest value was achieved by Red Cell Distribution Width-Standard Deviation parameter. The Sigma calculation based on Spanish TEa showed that seven CBC parameter achieved Sigma value ≥3. Conclusions According to the results of the study, it can be concluded that Sigma scores have a significant fluctuation based on which TEa sources are utilized and the need for Sigma metrics harmonization and standardization is highlighted. Additionally, low Sigma values of most CBC parameters are resulted in the conclusion that the use of performance goals depending on BV data is difficult for common clinical use. Therefore, clear standardized criteria are quite necessary for the selection of TEa goal by laboratories.

Candidate High-Resolution Mass Spectrometry-Based Reference Method for the Quantification of Procalcitonin in Human Serum Using a Characterized Recombinant Protein as a Primary Calibrator.

Procalcitonin (PCT) is a widely used biomarker for rapid sepsis diagnosis and antibiotic stewardship. Variability of results in commercial assays has highlighted the need for standardization of PCT measurements. An antibody-free candidate reference measurement procedure (RMP) based on the isotope dilution mass spectrometry and protein calibration approach was developed and validated to quantify PCT in human serum. The method allows quantification of PCT from 0.25 to 13.74 μg/L (R > 0.998) with extension up to 132 μg/L after dilution of samples with PCT concentration above 13.74 μg/L. Intraday bias was between −3.3 and +5.7%, and interday bias was between −3.0 and −0.7%. Intraday precision was below 5.1%, and interday precision was below 4.0%. The candidate RMP was successfully applied to the absolute quantification of PCT in five frozen human serum pools. A recombinant PCT used as a primary calibrator was characterized by high-resolution mass spectrometry and amino acid analysis to establish traceability of the results to the SI units. This candidate RMP is fit to assign target values to secondary certified reference materials (CRMs) for further use in external quality assessment schemes to monitor the accuracy and comparability of the commercially available immunoassay results and to confirm the need for improving the harmonization of PCT assays. The candidate RMP will also be used to evaluate whether the correlation between the candidate RMP and immunoassays is sufficiently high. Overall, this candidate RMP will support reliable sepsis diagnosis and guide treatment decisions, patient monitoring, and outcomes.

Beyond Diagnostics: The role of a RT-PCR laboratory in a pandemic

PurposeThe gold standard for the detection of SARS-CoV-2 is Real Time Reverse Transcriptase PCR (rRT-PCR). A combination of nasopharyngeal and oropharyngeal swabs improves the sensitivity of detection of SARS-CoV-2 in samples. The first wave of COVID-19 impacted Chennai in May 2020 and lasted till October 2020. The second wave began in March 2021 and lasted till June 2021. The aim of this study is to compare and analyze the COVID-19 waves in 2020 and 2021 based on the data from a tertiary care centre in Chennai, India.Methods & MaterialsA total of 42,374 samples were tested by rRT-PCR (Rotor Gene-Q) between March 2020 and June 2021. RNA was extracted using Zybio nucleic acid extraction kit. The target regions of the RT-PCR kits (ViroQ SARS CoV2, Bag Diagnostics, Germany) were the E-gene and RdRp gene. Quality control is maintained by routine participation in the external quality assurance scheme (EQAS).ResultsIn 2020, 22,905 samples were tested and 3,415 samples tested positive for COVID 19. During the first wave of COVID-19 between May-October 2020, 2989 samples tested positive for COVID 19. Between January and June 2021, 19,469 samples were tested and 2,320 samples were COVID-19 positive. A total of 2,155 samples were positive for COVID-19 in the second wave between March-June 2020. The duration of the first wave was longer with a smaller peak in incidence of COVID 19. The second wave in 2021 had a shorter duration with a more pronounced spike in COVID-19 cases in April 2021.ConclusionThe number of COVID 19 positive cases are similar between the two waves of COVID 19. However, the first wave of COVID-19 took place over a period of nearly six months, while the second wave occurred over three to four months. There is a noticeable surge in COVID-19 incidence observed in April-May 2021. This could indicate the increased infectivity of the virus as observed with the cases doubling rapidly during this time. Documenting the characteristics of the wave in terms of its rapidity of onset of disease and peaks in incidence would offer insight into the progression of COVID-19.

External quality control of microbiological testing in Polish medical diagnostic laboratories in 2020

<br><b>Introduction:</b>The paper presents the course of external quality control programmes organised in 2020 by the Centre of Quality Control in Microbiology (CQCM), including the 27<sup>th</sup> edition of the Polish National External Quality Assessment Scheme in Microbiology POLMICRO.</br> <br><b>Aim:</b>The assessment of the microbiological diagnostics’ quality carried out by Polish laboratories based on results of the POLMICRO, POLMICRO/MIKOLOGIA (MYCOLOGY), and POLMICRO/SSE programmes.</br> <br><b>Material and methods:</b>The participants’ responses from all rounds conducted in 2020 were analysed, i.e. five rounds of the POLMICRO programme, two rounds of the POLMICRO /MIKOLOGIA programme, and one round of POLMICRO/SSE.</br> <br><b>Results:</b>Positive evaluation in all rounds in the annual cycle were obtained by 90,1% of POLMICRO, 92,5% POLMICRO/MIKOLOGIA, and 100% POLMICRO/SSE participants.</br> <br><b>Conclusions:</b> Laboratories participating in the CQCM programmes demonstrated skills in the identification, antimicrobial susceptibility testing, and detection of resistance mechanisms of pathogenic microorganisms. The area of internal quality control of antimicrobial susceptibility testing requires improvement, especially the selection of reference strains.</br>

European interlaboratory comparison investigations (ICI) and external quality assurance schemes (EQUAS) for the analysis of bisphenol A, S and F in human urine: Results from the HBM4EU project

The Human Biomonitoring for Europe initiative (HBM4EU) aims to study the exposure of citizens to chemicals and potentially associated health effects. One objective of this project has been to build a network of laboratories able to answer to the requirements of European human biomonitoring studies. Within the HBM4EU quality assurance and quality control scheme (QA/QC), a number of interlaboratory comparison investigations (ICIs) and external quality assurance schemes (EQUASs) were organized to ensure data consistency, comparability and reliability. Bisphenols are among the prioritized substance groups in HBM4EU, including bisphenol A (BPA), bisphenol S (BPS) and bisphenol F (BPF) in human urine. In four rounds of ICI/EQUAS, two target concentration levels were considered, related to around P25 and P95 of the typical exposure distribution observed in the European general population. Special attention was paid to the conjugated phase II metabolites known to be most dominant in samples of environmentally exposed individuals, through the analysis of both native samples and samples fortified with glucuronide forms. For the low level, the average percentage of satisfactory results across the four rounds was 83% for BPA, 71% for BPS and 62% for BPF. For the high level, the percentages of satisfactory results increased to 93% for BPA, 89% for BPS and 86% for BPF. 24 out of 32 participating laboratories (75%) were approved for the analyses of BPA in the HBM4EU project according to the defined criterion of Z-scores for both low and high concentration levels in at least two ICI/EQUAS rounds. For BPS and BPF, the number of qualified laboratories was 18 out of 27 (67%) and 13 out of 28 (46%), respectively. These results demonstrate a strong analytical capability for BPA and BPS in Europe, while improvements may be needed for BPF.

Quantification of Antibiotics in Patient Samples: State of the Art in Standardization and Proficiency Testing.

For many antibiotics, the convenient one-fits-all dosing regimen had to be abandoned. Owing to highly variable pharmacokinetics, therapeutic drug monitoring has become an indispensable prerequisite. It is based on a suitable measuring method, sample materials, and standardization. Appropriate quality control including external quality assessment (EQA) is essential. For many antibiotics, EQAs have been established for many decades, whereas others have only lately been introduced. This article gives an insight into the state of the art regarding the therapeutic drug monitoring of antibiotics regarding standardization, EQAs, and reference measurement procedures (RMPs). An overview of the currently available international EQA schemes for antibiotics and a literature overview of available RMPs are given. EQAs including gentamicin and vancomycin have been offered by German providers for more than 25 years. The period 2000-2020 was selected for a detailed analysis. The experiences with a new EQA including linezolid, meropenem, and piperacillin are described. EQAs for gentamicin and vancomycin are provided in many countries. Those for linezolid, meropenem, and piperacillin do not seem to be very common. Most of the antibiotics monitored for decades are measured by commercially available assays. EQAs for linezolid, meropenem, and piperacillin introduced in 2018 were rapidly accepted in Germany. Methods reported in this study were HPLC based either with UV or mass spectrometric detection. The number of participants succeeding was comparable between UV and mass spectrometry. Candidate RMPs for gentamicin, vancomycin, and linezolid based on isotope dilution mass spectrometry were published. EQAs are offered regularly for many antibiotics worldwide. The results of EQAs in Germany generally compare well, but there is potential for improvement. Both immunoassays and HPLC-based methods work properly in EQAs evaluated in Germany. From a quality control perspective, fast and inexpensive methods may be selected without endangering the patient's health based on clinical needs.

Rate of Peripheral Blood Smear Examination Service Provision and its Barriers among Public Hospitals in Southern Ethiopia: A Mixed-Methods Study

Introduction: Peripheral blood smear examination is a vital hematological test for diagnosis and monitoring of blood disorders. Despite its substantial role in the management of communicable and non-communicable diseases, its utilization is low. We aimed to assess the rate of peripheral blood smear examination service provision and its barriers among public hospitals in southern Ethiopia. Method: A cross-sectional study was conducted from January 01 to March 31, 2019, in five public hospitals of Southern Ethiopia. Socio-demographic data was collected from patients and healthcare providers. Peripheral blood smears were prepared using capillary blood collected from 423 patients with abnormal complete blood cell count. The smears were stained with Wright’s stain and examined under microscope by 1000X magnification to detect and identify morphological abnormality in the blood cells. A key informant interview was done with healthcare providers. Health facilities were assessed using a standard checklist. The quantitative data were analyzed by SPSS version 20 software. The qualitative data were transcribed, categorized, and thematically analyzed. The results of descriptive analyzes are presented in tables and figures. Result: The rate of provision of peripheral blood smear examination service was 11.6%. Nearly 90% of the eligible patients did not receive this service. Relatively better rate of service provision was observed among hospitals with essential resources for the service, and those participating in Hematology external quality assurance scheme. Lack of training, shortage of laboratory supplies, and inadequate supportive supervision were identified as barriers to regularly provide peripheral blood smear examination service. Conclusion: Rate of peripheral blood smear examination service provision is low in the area. A large proportion of eligible patients missed the deserved service. Adequate laboratory supplies, training, and continued supportive supervision should be considered to improve the provision of this vital service.

External quality assessment for one-stage and chromogenic factor IX assays in samples containing Alprolix (rFIXFc) or Idelvion (rIX-FP) and evidence that UK National External Quality Assessment Scheme for blood coagulation samples are commutable with patient samples.

There may be clinically relevant differences between results of different FIX assays in samples containing extended half life FIX concentrates requiring regular surveillance of assay results through proficiency testing exercises. Control materials used in proficiency testing must be commutable, that is have the same inter-assay properties as those demonstrated by authentic clinical samples when measured by different analytical methods. We assessed relationships between results with different FIX assays and commutability of UK National External Quality Assessment Scheme (NEQAS) materials containing rIX-FP (Idelvion) or rFIXFc (Alprolix) by comparing results obtained using widely used one-stage and chromogenic assays during a proficiency testing exercise with results obtained when analysing a series of individual patient samples using the same assay systems. NEQAS samples prepared by addition of either Idelvion or Alprolix to FIX deficient plasma were sent to 76haemophilia centres in Europe. A total of 18 Idelvion and 22 Alprolix patient samples were assayed in a single centre. Two chromogenic and two one-stage assays were compared. The pattern of results obtained for NEQAS samples and patient samples was similar. In all cases, the NEQAS sample data point was within the scatter of patient sample data in plots of patient sample results showing one-stage assay results using Synthasil or Actin FS plotted against chromogenic assay results with Biophen or Rox chromogenic FIX kits. This indicates that the NEQAS samples containing Idelvion or Alprolix were commutable and therefore suitable for use in proficiency testing exercises.

Sigma metrics in quality control- An innovative tool

The clinical laboratory in today’s world is a rapidly evolving field which faces a constant pressure to produce quick and reliable results. Sigma metric is a new tool which helps to reduce process variability, quantitate the approximate number of analytical errors, and evaluate and guide for better quality control (QC) practices.To analyze sigma metrics of 16 biochemistry analytes using ERBA XL 200 Biochemistry analyzer, interpret parameter performance, compare analyzer performance with other Middle East studies and modify existing QC practices.This study was undertaken at a clinical laboratory for a period of 12 months from January to December 2020 for the following analytes: albumin (ALB), alanine amino transferase (SGPT), aspartate amino transferase (SGOT), alkaline phosphatase (ALKP), bilirubin total (BIL T), bilirubin direct (BIL D), calcium (CAL), cholesterol (CHOL), creatinine (CREAT), gamma glutamyl transferase (GGT), glucose (GLUC), high density lipoprotein (HDL), triglyceride (TG), total protein (PROT), uric acid (UA) and urea. The Coefficient of variance (CV%) and Bias % were calculated from internal quality control (IQC) and external quality assurance scheme (EQAS) records respectively. Total allowable error (TEa) was obtained using guidelines Clinical Laboratories Improvement Act guidelines (CLIA). Sigma metrics was calculated using CV%, Bias% and TEa for the above parameters. It was found that 5 analytes in level 1 and 8 analytes in level 2 had greater than 6 sigma performance indicating world class quality. Cholesterol, glucose (level 1 and 2) and creatinine level 1 showed >4 sigma performance i.e acceptable performance. Urea (both levels) and GGT (level 1) showed <3 sigma and were therefore identified as the problem analytes. Sigma metrics helps to assess analytic methodologies and can serve as an important self assessment tool for quality assurance in the clinical laboratory. Sigma metric evaluation in this study helped to evaluate the quality of several analytes and also categorize them from high performing to problematic analytes, indicating the utility of this tool. In conclusion, parameters showing lesser than 3 sigma need strict monitoring and modification of quality control procedure with change in method if necessary.

A framework for evaluating the frequency of external quality assessment challenges

Background and aimsNo clear rules about the optimal frequency of organizing External Quality Assessment (EQA) rounds exist. More frequent challenges will facilitate faster responses and more reliable statistics. Adding extra samples leads to extra information, but the correlation between results from different samples reduces the extra information from additional samples. Materials and MethodsData were used for ALT and Albumin from the RCPAQAP EQA scheme. Every two weeks, laboratories analysed two samples. Correlation between results of different samples was calculated to determine the power of distinguishing poorly from well-performing laboratories. The power was compared to hypothetical cases of no correlation and one-sample-per-week to estimate the number of samples negated due to correlation. ResultsCorrelation leads to negation of a number of samples, but not more than 50% of samples were negated. The number of negated samples was positively related with the correlation between EQA results. ConclusionsThe proposed framework provides a quantitative evaluation of the impact of adding more EQA rounds or samples. A correlation exists and is higher for analyses performed closer in time, but the examples shown here did not show a detrimental effect on correctly evaluating laboratories.

External Quality Assurance Schemes (Equass) and Inter-Laboratory Comparison Investigations (Icis) for Human Biomonitoring of Polycyclic Aromatic Hydrocarbon (Pah) Biomarkers in Urine as Part of the Quality Assurance Programme Under Hbm4eu

External Quality Assurance Schemes (Equass) and Inter-Laboratory Comparison Investigations (Icis) for Human Biomonitoring of Polycyclic Aromatic Hydrocarbon (Pah) Biomarkers in Urine as Part of the Quality Assurance Programme Under Hbm4eu