Interlaboratory Coefficient Of Variation Research Articles

A-135 Assessment of Inter-Laboratory Variation in Biochemistry Parameters in Mongolian Clinical Laboratories: A Twelve-Year Analysis

Abstract Background External quality assessment (EQA) is essential for evaluating the performance of clinical laboratories and improving the quality of their analytical procedures. The Mongolian External Quality Assessment Scheme (MEQAS) has been established by organizations under the Ministry of Health to fulfill this purpose. The aim of this study is to provide a comprehensive summary of the inter-laboratory variation in biochemistry parameters among laboratories in Mongolia over a twelve-year period. Methods Three types of control materials were utilized: QAP-Trol Normal and Pathological levels, manufactured by Sysmex, and Pooled serum, prepared by combining leftover serum of patients. Samples were distributed semi-annually to laboratories, with participants measuring them promptly within three days. Results for 23 biochemistry parameters were submitted within a week via the “SmartEqas” software, enabling for analysis based on method and analyzer, and calculating standard deviation index (SDI), coefficient of variation (CV), and bias percentage (Bias%). Results In comparing the initial and most recent surveys, the number of participants has increased by nearly four times, rising from 55 to 217. Notably, the proportion of fully automatic users surged from 23.6% to 86.6%, a trend attributed to the establishment of numerous new laboratories and a growing recognition of the importance of EQA. Changes in the inter-laboratory coefficient of variation (CV) for each parameter were assessed from the initial to the recent period by calculating the mean of changes. In the recent assessments, CVs decreased to less than 10% for 14 parameters, including AST, ALT, UN, CRE, GLU, and others. Certain parameters, such as K, GLU, and Urea, exhibited markedly reduced variation from 16.3%, 12.1%, and 22.2% to 2.9%, 7.4%, and 9.3%, respectively. Conversely, some parameters, including LD (L-P), GGT, AMY (1), ALP (2), UA, TBIL, DBIL, FE, and MG, displayed gradual reductions in CVs to 10-20% compared to the initial period. In contrast, the coefficient of variation (CV) for four parameters: LD (P-L), AMY (2), ALP (3), and ALP (4), has not shown significant decreases and remains high, exceeding 20%. Conclusions Despite participation not being mandatory, laboratories in Mongolia exhibit a strong willingness to engage in the assessment process. The implementation of MEQAS has yielded tangible benefits, a reduction in inter-laboratory variation for most biochemistry parameters, with some achieving international level. While this improvement can be attributed to the streamlining of measurement methods, similar to outcomes observed in other countries, it is important to acknowledge the persistence of random and systematic errors. However, it is worth noting that certain parameters still exhibit higher CVs compared to similar studies. This discrepancy may be attributed to the inherent variation in enzymes among different methods and manufacturers. Hence, there is a clear need for continuous improvement measures and knowledge-sharing initiatives with other nations to address these challenges. Evaluating and implementing such measures at the national level will further enhance the quality of medical care in Mongolia.

Coagulation factors VIII and factors IX testing practices in China: Results of the 5-year external quality assessment program

Background and aimsTesting for coagulation factors VIII (FVIII) and IX (FIX) plays significant importance in the diagnostic and treatment of hemophilia A and B. External quality assessment (EQA) scheme aimed to assess the participants’ performance of testing for coagulation factors and identify shortcomings in clinical practice. This study aimed to investigate the performance trends of the participating laboratories in China national external quality assessment Scheme (China NEQAS) for FVIII and FIX over a five-year period (2019–2023). Materials and methodsA total of ten external quality assessment (EQA) rounds were conducted from 2019 to 2023 in the China NEQAS for FVIII and FIX. The distribution of method, reagent and instrument were calculated. The trends of method- specific inter-laboratory coefficient of variation (CV) and pass rates were analyzed over 5 years. The dilutions for coagulation factor testing were also investigated. ResultsAll laboratories use one-stage assays to detect FVIII and FIX activity. The inter-laboratory overall CV decreased year by year (10.9 % to 9.3 % for FVIII and 13.5 % to 10.2 % for FIX), and the laboratory pass rate steadily increased (88.0 % to 93.4 % for FVIII and 81.3 % to 92.7 % for FIX). The majority of laboratories employed a single dilution methodology for the assessment of FVIII and FIX activity. The interlaboratory CV was elevated for the Siemens reagent (Actin FSL) during analysis of moderately abnormal FIX concentrations of EQA samples in most batches. ConclusionsThe implementation of the external quality assessment has contributed to facilitate the enhancement of testing quality. Chromogenic assay is a supplement to accurate determination when necessary. Laboratories may choose to perform dilution tests or direct assays to identify the presence of inhibitors, particularly when they are suspected.

Evaluation of blood lead measurements by the 6-year external quality assessment program in China

BackgroundBlood lead is an important clinical indicator. A typical tool for promoting standardisation or harmonisation is external quality assessment (EQA). Therefore, the National Centre for Clinical Laboratories (NCCL) in China launched the EQA Program for blood lead measurement in 2006 to assess its standardisation process. MethodsBlood lead EQA samples tested for homogeneity and stability were sent to participating laboratories. The return data were grouped according to the detection method. The robust mean value, robust coefficient of variation (CV) and standard uncertainty were calculated according to ISO 13528. The evaluation criteria were determined based on a thorough analysis of the previous pass rate and the current detection level. Overall trends in the blood lead EQA program over 6 years were investigated by calculating the pass rates of participating laboratories. We compared the pass rates and current issues of different detection methods and analysed the target values, bias and CV results of mainstream detection methods. ResultsA total of 4,283 laboratories participated in EQA programs from 2017 to 2022. The pass rates were generally increasing while the inter-laboratory mean CVs were decreasing. For samples with varying concentrations, the higher the concentration, the smaller the CV. According to the evaluation criteria, the most used measurement methods, Graphite Furnace Atomic Absorption Spectrometry (GFAAS) and Tungsten Ship Atomic Absorption Spectrometry (TSAAS) demonstrated better performances than Differential Potentiometric Stripping (DPS), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Flame Atomic Absorption Spectrometry (FAAS). Furthermore, DPS, ICP-MS and FAAS outperformed Anodic Stripping Voltammetry (ASV). ConclusionOur study provides reliable information on the standardisation of blood lead measurement procedures for manufacturers and clinical laboratories. Further improvements for standardisation are still required to make laboratories more patient-centred.

Analytical Performance of Different Laboratory Methods for Measuring Susoctocog-Alfa.

Recombinant porcine factor VIII (rpFVIII) is indicated for treating bleeding episodes in acquired haemophilia A, but there are few data regarding laboratory methods to adequately monitor treatment. This study involving three Italian laboratories aimed to evaluate the analytical performance of different assays for measuring rpFVIII. Five spiked rpFVIII samples (0.5–1.5 IU/mL) were analysed on three days, in triplicate, with eleven combinations of reagents (Werfen, Boston, MA, USA: SynthasIL and SynthaFax for one-stage assay, Chromogenix Coamatic FVIII for chromogenic assay), FVIII depleted plasmas (with or without von Willebrand factor—VWF) and calibrators (HemosIL human calibrator plasma, porcine calibrator diluted in FVIII deficient plasma with or without VWF). The assays were performed on ACL TOP analysers (Werfen, Boston, MA, USA). Intra- and inter-assay and inter-laboratory Coefficient of Variation (CV%) were calculated together with percentage of recovery (% recovery) on the expected value. The results showed that the reagent combinations reaching satisfactory analytical performance are: SynthasIL/human calibrator/deficient plasma+VWF (total recovery 99.4%, inter-laboratory CV 4.04%), SynthasIL/porcine calibrator/deficient plasma+VWF (total recovery 111%, inter-laboratory CV 2.75%) and Chromogenic/ porcine calibrator/deficient plasma+VWF (total recovery 96.6%, inter-laboratory CV 8.32%). This study highlights that the use of porcine standard (when available) and FVIII deficient plasma with VWF should be recommended.

Development a high-throughput zebrafish embryo acute toxicity testing method based on OECD TG 236

The Organization for Economic Co-operation and Development (OECD）Test Guideline (TG) 236 for zebrafish embryo acute toxicity testing was adopted for chemical toxicity assessment in 2013. Due to the increasing demand for prediction and evaluation of the acute toxicity using zebrafish embryos, we developed a method based on OECD 236 test guideline with the aim to improve the testing efficiency. We used 4–128 cell stage zebrafish embryos and performed an exposure assay in a 96-well microtiter plate, observing the lethality endpoints of embryos at 48-h postexposure. A total of 32 chemicals (two batches) were used in the comparison study. Our results indicated that the logarithmic LC50 (half lethal concentration) obtained by the modified method exhibited good correlation with that obtained by the OECD 236 testing method, and the R2 of the linear regression analysis was 0.9717 (0.9621 and 0.9936 for the two batches, respectively). Additionally, the intra- and inter-laboratory coefficient of variation (CVs) for the LC50 from the testing chemicals (17 chemicals in second batch) was less than 30%, except for CuSO4. Therefore, the developed method was less time-consuming and demonstrated a higher throughput for toxicity testing compared to the prior method. We argue the developed method could be used as an additional choice for high-throughput zebrafish embryo acute toxicity test.

Interlaboratory Performance in Measurement of Dabigatran and Rivaroxaban.

Assessing direct oral anticoagulant (DOAC) drug levels by reliable laboratory assays is necessary in a number of clinical scenarios. To evaluate the performance of DOAC-specific assays for various concentrations of dabigatran and rivaroxaban, assess the interlaboratory variability in measurement of these DOACs, and investigate the responsiveness of the routine clotting assays to various concentrations of these oral anticoagulants. College of American Pathologists proficiency testing survey data from 2013 to 2016 were summarized and analyzed. For dabigatran, the interlaboratory coefficient of variation (CV) of ecarin chromogenic assay was broad (ranging from 7.5% to 29.1%, 6.3% to 15.5%, and 6.8% to 9.0% for 100-ng/mL, 200-ng/mL, and 400-ng/mL targeted drug concentrations, respectively). The CV for diluted thrombin time for dabigatran was better overall (ranging from 11.6% to 17.2%, 9.3% to 12.3, and 7.1% to 11.2% for 100 ng/mL, 200 ng/mL, and 400 ng/mL, respectively). The rivaroxaban-calibrated anti-Xa assay CVs also showed variability (ranging from 11.5% to 22.2%, 7.2% to 10.9%, and 6.4% to 8.1% for 50-ng/mL, 200-ng/mL, and 400-ng/mL targeted drug concentrations, respectively). The prothrombin time (PT) and activated partial thromboplastin time (aPTT) showed variable dose- and reagent-dependent responsiveness to DOACs: PT was more responsive to rivaroxaban and aPTT to dabigatran. The undiluted thrombin time showed maximum prolongation across all 3 dabigatran concentrations, making it too sensitive for drug-level monitoring, but supporting its use as a qualitative screening assay. DOAC-specific assays performed reasonably well. While PT and aPTT cannot be used safely to determine DOAC degree of anticoagulation, a normal thrombin time excludes the presence of dabigatran.

External quality control and training of semen analysis in the Netherlands: starting point for further reduction of outcome variability.

Semen analysis is characterized by high levels of intra- and inter-laboratory variability, due to a low level of standardization, high subjectivity of the assessments, and problems with automated procedures. To improve consistency of laboratory results, quality control and training of technicians are important requisites. The goals of this study are to evaluate the results of an external quality control (EQC) program and standardized training by ESHRE Basic Semen Analysis Courses (BSAC) on the variability in manual assessments of semen parameters. We performed retrospective analyses of (1) the interlaboratory variability in the Dutch EQC program and (2) the interobserver variability in BSACs for concentration, motility, and morphology assessments. EQC data showed that the interlaboratory coefficient of variation (CV) for concentration assessment decreased (range from 24.0%–97.5% to 12.7%–20.9%) but not for morphology and motility assessments. Concentration variability was lower if improved Neubauer hemocytometers were used. Morphology assessment showed highest CVs (up to 375.0%), with many outliers in the period of 2007–2014. During BSAC, a significant reduction of interobserver variability could be established for all parameters (P < 0.05). The absence of an effect in the EQC program for motility and morphology might be explained by respectively the facts that motility assessment was introduced relatively late in the EQC program (since 2013) and that criteria for morphology assessment changed in time. BSAC results might have been influenced by the pretraining level of participants and the influence of external factors. Both EQC and training show positive effects on reducing variability. Increased willingness by laboratories to change their methods toward standards may lead to further improvements.

Interlaboratory comparison of microplastic extraction methods from marine biota tissues: A harmonization exercise of the Plastic Busters MPAs project

In the framework of the Plastic Busters MPAs project, a harmonization exercise on two methods of microplastic extraction from biological samples i.e. 15% H2O2 digestion and 10% KOH digestion was carried out. The two methods were tested in four laboratories on fish gastrointestinal tracts and mussel tissues spiked with polyethylene, polypropylene and polyethylene terephthalate. The recovery percentage of microplastics for each method, species and polymer tested were overall similar among laboratories, and interlaboratory coefficient of variation was less than 11% for the majority of samples. Microplastic recovery rates for the two methods were similar for each sample tested, but overall mean interlaboratory recovery rate using KOH (96.67%) was higher than H2O2 (88.75%). Results validate the use of both methods for extracting microplastics from biota tissues. However, when comparing the two methods in terms of microplastic recovery rate, time consumed, technical difficulties and cost, digestion with 10% KOH is considered optimal.

The results of external quality assessment programme on urine leukocyte and erythrocyte counting in Poland.

IntroductionUrine particle analysis is an important diagnostic tool. The aim of this study was to evaluate the quality of urine leukocyte (WBC) and erythrocyte (RBC) counting results obtained with manual and automated methods in Polish laboratories participating in the international external quality assessment (EQA) programme.Materials and methods1400 WBC and RBC counting results were obtained from 183 laboratories in EQA surveys organised by Labquality (Helsinki, Finland) from 2017 to 2019. The between-laboratory coefficient of variation (CV), the percentage difference between the laboratories' results and target values (Q-score (%)), as well as modified Youden plots were analysed.ResultsFor automated method groups, the medians of inter-laboratory CVs varied from 14% to 33% for WBC counting and from 10% to 39% for RBC counting. For manual method groups, the medians of CV varied from 53% to 71% (WBC) and from 55% to 70% (RBC), and they were significantly higher, in comparison to CVs for most automated method groups (P < 0.001). The highest percentage of results outside the target limits (36%) and the highest range of Q-score (%) (from - 93% to 706%) were observed for laboratories which participated in the surveys for the first or second time. The percentage of deviating results and the ranges of Q-score decreased with an increased frequency of laboratories’ participation in the surveys.ConclusionsThe quality of manual methods of urine WBC and RBC counting is unsatisfactory. There is an urgent need to take actions to improve laboratories’ performance and to increase harmonisation of the results.

Standardized protocol for determination of biohydrogen potential

Biohydrogen production potential (BHP) depends on several factors like inoculum source, substrate, pH, among many others. Batch assays are the most common strategy to evaluate such parameters, where the comparison is a challenging task due to the different procedures used. The present method introduces the first internationally validated protocol, evaluated by 8 independent laboratories from 5 different countries, to assess the biohydrogen potential. As quality criteria, a coefficient of variation of the cumulative hydrogen production (Hmax) was defined to be <15 %. Two options to run BHP batch tests were proposed; a manual protocol with periodic measurements of biogas production, needing conventional laboratory materials and analytical equipment for biogas characterization; and an automatic protocol, which is run in a device developed for online measurements of low biogas production. The detailed procedures for both protocol options are presented, as well as data validating them. The validation showed acceptable repeatability and reproducibility, measured as intra- and inter-laboratory coefficient of variation, which can be reduced up to 9 %.

Reliability of In Vitro Methods Used to Measure Intrinsic Clearance of Hydrophobic Organic Chemicals by Rainbow Trout: Results of an International Ring Trial.

In vitro assays are widely employed to obtain intrinsic clearance estimates used in toxicokinetic modeling efforts. However, the reliability of these methods is seldom reported. Here we describe the results of an international ring trial designed to evaluate two in vitro assays used to measure intrinsic clearance in rainbow trout. An important application of these assays is to predict the effect of biotransformation on chemical bioaccumulation. Six laboratories performed substrate depletion experiments with cyclohexyl salicylate, fenthion, 4-n-nonylphenol, deltamethrin, methoxychlor, and pyrene using cryopreserved hepatocytes and liver S9 fractions from trout. Variability within and among laboratories was characterized as the percent coefficient of variation (CV) in measured in vitro intrinsic clearance rates (CLIN VITRO, INT; ml/h/mg protein or 106 cells) for each chemical and test system. Mean intralaboratory CVs for each test chemical averaged 18.9% for hepatocytes and 14.1% for S9 fractions, whereas interlaboratory CVs (all chemicals and all tests) averaged 30.1% for hepatocytes and 22.4% for S9 fractions. When CLIN VITRO, INT values were extrapolated to in vivo intrinsic clearance estimates (CLIN VIVO, INT; l/d/kg fish), both assays yielded similar levels of activity (<4-fold difference for all chemicals). Hepatic clearance rates (CLH; l/d/kg fish) calculated using data from both assays exhibited even better agreement. These findings show that both assays are highly reliable and suggest that either may be used to inform chemical bioaccumulation assessments for fish. This study highlights several issues related to the demonstration of assay reliability and may provide a template for evaluating other in vitro biotransformation assays.

Harmonization of urine albumin/creatinine ratio (ACR) results: a study based on an external quality assessment program in Polish laboratories.

Abstract Background: The ratio of albumin to creatinine (ACR) is an important parameter used for detection of albuminuria in patients with early kidney damage. The aim of the study was to evaluate the harmonization of ACR results among Polish participants in an international external quality assessment (EQA) program, and to evaluate the impact of albumin and creatinine analytical performance on the harmonization of ACR results. Methods: We analyzed 182 results of albumin, 202 of creatinine, and 180 of ACR obtained from Polish laboratories in an EQA program organized by Labquality. The dispersion of the results in surveys and percentage differences between the results and target values were calculated. Moreover, differences between method groups were assessed. Results: The inter-laboratory coefficient of variation (CV) for ACR was 36%. Only 74% of results of Polish laboratories were within the target limits; for 11% of the results, an incorrect albuminuria category would have been reported. The inter-laboratory CV for albumin was 20%, 2.6-fold higher than for creatinine. Significant differences between method groups for albumin determination have been observed, even when the same measurement technique was used. The greatest difference between two groups was 23%, 2.5-fold greater in comparison to creatinine. Conclusions: There is an insufficient harmonization of ACR values among Polish laboratories, caused mainly by urine albumin analytical performance. Given the important role of ACR in the classification, monitoring and treatment of kidney damage, the harmonization of albumin measurements is crucial and urgently needed.

Centrally Determined Standardization of Flow Cytometry Methods Reduces Interlaboratory Variation in a Prospective Multicenter Study.

Objectives:Flow cytometry (FC) aids in characterization of cellular and molecular factors involved in pathologic immune responses. Although FC has potential to facilitate early drug development in inflammatory bowel disease, interlaboratory variability limits its use in multicenter trials. Standardization of methods may address this limitation. We compared variability in FC-aided quantitation of T-cell responses across international laboratories using three analytical strategies.Methods:Peripheral blood mononuclear cells (PBMCs) were isolated from three healthy donors, stimulated with phorbol 12-myristate 13-acetate and ionomycin at a central laboratory, fixed, frozen, and shipped to seven international laboratories. Permeabilization and staining was performed in triplicate at each laboratory using a common protocol and centrally provided reagents. Gating was performed using local gating with a local strategy (LGLS), local gating with a central strategy (LGCS), and central gating (CG). Median cell percentages were calculated across triplicates and donors, and reported for each condition and strategy. The coefficient of variation (CV) was calculated across laboratories. Between-strategy comparisons were made using a two-way analysis of variance adjusting for donor.Results:Mean interlaboratory CV ranged from 1.8 to 102.1% depending on cell population and gating strategy (LGLS, 4.4–102.1% LGCS, 10.9–65.6% CG, 1.8–20.9%). Mean interlaboratory CV differed significantly across strategies and was consistently lower with CG.Conclusions:Central gating was the only strategy with mean CVs consistently lower than 25%, which is a proposed standard for pharmacodynamic and exploratory biomarker assays.

Evaluation of dabigatran, rivaroxaban and apixaban target-specific assays in a multicenter French study

Dabigatran etexilate, rivaroxaban and apixaban (DOACs) are widely used and measurement of their concentration is desirable in certain clinical situations. Target-specific assays are available but limited information exists on their performance especially in their ability to accurately measure low and high concentrations. AimsTo define, in a multicenter study, the precision and accuracy of DOAC measurements in daily practice. Methods15 plasma samples (kindly provided by Hyphen-Biomed) spiked with 5 blinded concentrations of dabigatran, rivaroxaban or apixaban (targeted 0–40–100–250–500ng/mL, actual concentrations measured by HPLC-MS/MS), were sent to 30 haemostasis laboratories. DOAC concentration, PT and aPTT were measured once in each sample using local reagents. Interlaboratory precision was determined by its coefficient of variation (CV) and accuracy by its bias. Results464 DOAC measurements were performed in the 30 laboratories using 4 dabigatran and 5 rivaroxaban/apixaban calibrated assays on 3 analysers. Inter-laboratory CVs were below 18% for concentrations ≥100ng/mL, and higher for concentrations ~40ng/mL; biases were below 8% for all drugs and concentrations. In DOAC-free samples, concentrations were all below the lower limit of quantification except for one value (dabigatran: 35ng/mL). Depending on the concentrations, significant differences were found between reagents in rivaroxaban and apixaban concentration values. PT and aPTT ratios displayed a low sensitivity to apixaban. ConclusionOur results suggest that calibrated DOAC assays allow the reliable measurement of a wide range of drug concentrations, even though improvement of their performances is necessary, especially for measuring low concentrations.

External quality assessment program for detection of glucose-6-phosphate dehydrogenase deficiency in the Guangxi region.

The aim of this study is to improve the quality of testing for glucose-6-phosphate dehydrogenase (G6PD) deficiency through evaluation and analysis of the laboratory tests for G6PD activity. External quality assessment (EQA) was carried out twice per year with five samples each from 2014 to 2016. Samples were used for quantitative and qualitative assays. Quantitative results were collected, qualitative results were determined with reference values, and information about methods, reagents and instruments from participating laboratories within the required time. Laboratory performance scores, coefficient of variation (CV), and the rates of false negative and positive results were calculated. As a result, a total of 2,834 cases of negative quality control (QC) samples and 2,451 cases of positive QC samples were assessed, where the rates of false negative and false positive results were 1.31% (37/2,834) and 1.34% (33/2,451), respectively. Quantitative results indicated an increasing trend in testing quality, which were consistent with conclusions based on the comparison of EQA full-score and acceptable ratio in six assessments. The 2nd assay in 2016 had the best full-score ratio of 68.9% (135/196) and best acceptable ratio of 84.2% (165/196). There was a decreasing trend in the average CV of six reagents produced in China, and the range of average CV increased to 14.6–23.6% in 2016. The average CV of low level and high level samples was 22.5% and 15.3%, respectively, demonstrating that samples with low G6PD activity have greater interlaboratory CV values. In conclusion, laboratories improved their testing quality and provided better diagnostic service for G6PD deficiency in areas with high incidence after participation in the EQA program in the Guangxi region.

Interlaboratory Reproducibility of a Targeted Metabolomics Platform for Analysis of Human Serum and Plasma.

A critical question facing the field of metabolomics is whether data obtained from different centers can be effectively compared and combined. An important aspect of this is the interlaboratory precision (reproducibility) of the analytical protocols used. We analyzed human samples in six laboratories using different instrumentation but a common protocol (the AbsoluteIDQ p180 kit) for the measurement of 189 metabolites via liquid chromatography (LC) or flow injection analysis (FIA) coupled to tandem mass spectrometry (MS/MS). In spiked quality control (QC) samples 82% of metabolite measurements had an interlaboratory precision of <20%, while 83% of averaged individual laboratory measurements were accurate to within 20%. For 20 typical biological samples (serum and plasma from healthy individuals) the median interlaboratory coefficient of variation (CV) was 7.6%, with 85% of metabolites exhibiting a median interlaboratory CV of <20%. Precision was largely independent of the type of sample (serum or plasma) or the anticoagulant used but was reduced in a sample from a patient with dyslipidaemia. The median interlaboratory accuracy and precision of the assay for standard reference plasma (NIST SRM 1950) were 107% and 6.7%, respectively. Likely sources of irreproducibility were the near limit of detection (LOD) typical abundance of some metabolites and the degree of manual review and optimization of peak integration in the LC-MS/MS data after acquisition. Normalization to a reference material was crucial for the semi-quantitative FIA measurements. This is the first interlaboratory assessment of a widely used, targeted metabolomics assay illustrating the reproducibility of the protocol and how data generated on different instruments could be directly integrated in large-scale epidemiological studies.

Inter-laboratory proficiency tests in measuring thermal insulation and evaporative resistance of clothing using the Newton-type thermal manikin

Clothing acts as an important barrier for heat and vapor transfer between the human body and the environment. Parameters that could describe that transfer include, inter alia, thermal insulation (the so-called dry heat exchange) and evaporative resistance (the so-called wet heat exchange). Once the above-mentioned parameters are determined, it is possible to consciously adapt clothing ensembles to the existing thermal environment in the workplace. In order to validate the mentioned method of thermal insulation and evaporative resistance measurements, proficiency tests (PTs) were organized. The main goal of the PT was to compare thermal insulation and evaporative resistance for one set of clothing using the Newton-type thermal manikin. In total, four laboratories participated in the PT study. The reference value of the thermal insulation ( It) and evaporative resistance ( Ret) were calculated as the mean of all the results. The assessment criteria included permissible errors for thermal insulation and evaporative resistance measurements, which were 4% and 10%, respectively. Calculations included, inter alia, z-scores and indicators, such as the inter-laboratory coefficient of variation or the reproducibility limit. The results contribute to the worldwide discussion on standardized studies of evaporative resistance of clothing.

Interlaboratory Variation in CD34+ Cell Quantification in Low Risk Myelodysplastic Syndromes

Background: Accurate bone marrow (BM) blast count is essential for establishing prognosis in lower-risk myelodysplastic syndromes (MDS). Flow cytometry immunophenotyping (FCI) helps to evaluate the most immature BM cell compartment, but it is not known whether the CD34+ myeloid cell count in MDS are comparable among different observers. We investigated the FCI approaches used for enumeration of CD34 + myeloid cells in MDS in the routine practice in 6 clinical Spanish centers, and then explored if data were reproducible among participants.Methods: In this prospective study, participants exchanged 47 FCI files from MDS BM samples with <5% blasts, and quantified the CD34+ myeloid cells in a blind manner. No agreement regarding cytometers, number, reagents, fluorochromes and events recorded were previously established.Results: The mAb combinations selected to identify BM myeloid CD34+ cells was highly variable: CD45 was included in 45/47 (95.7%) files, CD34/CD45/CD117 in 37 (78.7%), and HLA-DR in 19 files (40.4%). The FCI assays used in every centre were quite different, but a very good concordance among the 6 FCI observers for CD34+ cell enumeration was observed with the intraclass correlation coefficient (0.720). Considering the specific analysis of each sample, 2 groups were distinguished. Twenty-five cases (53.2%) exhibited the highest concordance, with an interlaboratory coefficient of variation (CV) <30%, or a difference among observers <0.5%. In the remaining 22 cases, the concordance among participants was low. Comparison of the characteristics of high and low agreement assays showed no statistical differences. In order to determine whether the lower concordance obtained among observers after the analysis of these 22 samples could be improved, we designed a protocol with specific guidelines with gating strategies for identification of the CD34+ myeloid cells in several consecutive steps. The strategy was designed for samples with the CD34/CD45/CD117 mAb combination (n=15), with or without HLADR. Using this strategy, the interlaboratory CV improved in 7/15 cases (46.66%), but no improvement was obtained in the remaining 8 cases. Finally, the percentage of CD34+ myeloid cells was reproducible in 32/47 cases (68%) diagnosed with low risk MDS. Conclusions: Despite different methodology, accuracy among observers in CD34 cell quantification is feasible. Selection of appropriate protocols and targeted training would help to enhance the reproducibility of the technique among different observers. However, the intrinsic heterogeneity of these cells in MDS might justify the difficulty for their identification in some cases. DisclosuresNo relevant conflicts of interest to declare.

Commentary: The reliability of telomere length measurements

Commentary: The reliability of telomere length measurements

The Platelet Function Analyser (PFA)-100 and von Willebrand disease: a story well over 16 years in the making.

The Platelet Function Analyser (PFA)-100 and von Willebrand disease: a story well over 16 years in the making.