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The diagnostic approach to hypopituitarism involves many disciplines. Clinical symptoms rarely are specific. Imaging techniques are helpful but cannot prove the specific functional defects. Therefore, the definitive diagnosis of pituitary insufficiency is largely based on laboratory tests. However, also laboratory methods come with inherent limitations, and it is essential for the clinician to know and recognize typical pitfalls. Most factors potentially impairing the quality of hormone measurements are introduced in the preanalytical phase, i.e. before the hormones are measured by the laboratory. For example, the timing of blood drawing with respect to circadian rhythm, stress, and medication can have an influence on hormone concentrations. During the actual analysis of the hormones, cross-reactions with molecules present in the sample presenting the same or similar epitopes than the intended analyte may affect immunoassays. Interference can also come from heterophilic or human anti-animal antibodies. Unexpected problems can also be due to popular nutritional supplements which interfere with the measurement procedures. An important example in this respect is the interference from biotin. It became only clinically visible when the use of this vitamin became popular among patients. The extreme serum concentrations reached when patients take it as a supplement can lead to incorrect measurements in immunoassays employing the biotin-streptavidin system. To some extent, hormone analyses using liquid chromatography mass spectrometry (LCMS) can overcome problems, although availability and cost-effectiveness of this method still imposes restrictions. In the post-analytical phase, appropriateness of reference intervals and cut-offs with respect to the specific analytical method used is of outmost importance. Furthermore, for interpretation, additional biological and pharmacological factors like BMI, age and concomitant diseases must be considered to avoid misinterpretation of the measured concentrations. It is important for the clinician and the laboratory to recognize when one or more laboratory values do not match the clinical picture. In an interdisciplinary approach, the search for the underlying cause should be initiated. [ABSTRACT FROM AUTHOR]

The assessment of homogeneity of liquids in storage tanks is crucial for quality control products, commercial relations and a salient technological challenge facing the petroleum industry. This study describes a method used in the Brazilian oil industry to estimate if there is significant (vertical) segregation in large storage tanks. Here, a method based on experimental design and classical ANOVA for analyzing the experimental data to arrive at a better method to estimate if there is statistically significant segregation within the storage tanks (lack of significance is called homogeneity in the paper) was used. Although ANOVA is a suitable tool for this purpose, the results were analyzed in more detail to propose a practical method that can be used routinely. Mechanical use of the ANOVA tests may easily lead to wrong conclusions. [ABSTRACT FROM AUTHOR]

Abstract Background Urinary protein:creatinine ratio (UPC) results affect the diagnosis, prognosis, and therapy of chronic kidney disease in cats. Objectives To investigate the interlaboratory and intralaboratory variability and the effect of storage on UPC and International Renal Interest Society (IRIS) proteinuria substaging in cats. Animals Healthy and diseased client‐owned cats. Methods Prospective study. Urine of 60 cats was randomly sent to 4 (of 9) participating laboratories (to assess interlaboratory variability) and per cat, 2 laboratories each received 2 aliquots (to determine intralaboratory variability). Samples of 23 cats were analyzed in the same laboratory the day of collection, after preservation at 22°C for 1 day and at 4°C during 1‐7 days (short‐term storage) and at −24°C and −80°C for 6‐12 months (long‐term storage). Storage conditions were compared by equivalence testing. Results UPCs showed good interclass correlation (ICC‐inter, 0.90) and excellent intraclass correlation (ICC‐intra, 0.99). However, in 30/60 (50%) cats at least 1 of 4 laboratories assigned a different IRIS proteinuria substage. Urinary protein:creatinine ratio remained stable with short‐term storage, but not after 6 months storage at −24°C and after 12 months storage at −24°C or −80°C. Long‐term storage caused a change in IRIS proteinuria substage in 27% of cats, whereas a shift occurred only in 4% of cats during short‐term storage. Conclusions and Clinical Importance Laboratory choice for UPC measurement can result in different IRIS substaging for the same cat, whereas urine storage at room temperature for 1 day or in the refrigerator for up to 7 days does not clinically affect UPC.

Any large dataset can be analyzed in a number of ways, and it is possible that the use of different analysis strategies will lead to different results and conclusions. One way to assess whether the results obtained depend on the analysis strategy chosen is to employ multiple analysts and leave each of them free to follow their own approach. Here, we present consensus-based guidance for conducting and reporting such multi-analyst studies, and we discuss how broader adoption of the multi-analyst approach has the potential to strengthen the robustness of results and conclusions obtained from analyses of datasets in basic and applied research.

Background: Urinary protein:creatinine ratio (UPC) results affect the diagnosis, prognosis, and therapy of chronic kidney disease in cats. Objectives: To investigate the interlaboratory and intralaboratory variability and the effect of storage on UPC and International Renal Interest Society (IRIS) proteinuria substaging in cats. Animals: Healthy and diseased client‐owned cats. Methods: Prospective study. Urine of 60 cats was randomly sent to 4 (of 9) participating laboratories (to assess interlaboratory variability) and per cat, 2 laboratories each received 2 aliquots (to determine intralaboratory variability). Samples of 23 cats were analyzed in the same laboratory the day of collection, after preservation at 22°C for 1 day and at 4°C during 1‐7 days (short‐term storage) and at −24°C and −80°C for 6‐12 months (long‐term storage). Storage conditions were compared by equivalence testing. Results: UPCs showed good interclass correlation (ICC‐inter, 0.90) and excellent intraclass correlation (ICC‐intra, 0.99). However, in 30/60 (50%) cats at least 1 of 4 laboratories assigned a different IRIS proteinuria substage. Urinary protein:creatinine ratio remained stable with short‐term storage, but not after 6 months storage at −24°C and after 12 months storage at −24°C or −80°C. Long‐term storage caused a change in IRIS proteinuria substage in 27% of cats, whereas a shift occurred only in 4% of cats during short‐term storage. Conclusions and Clinical Importance: Laboratory choice for UPC measurement can result in different IRIS substaging for the same cat, whereas urine storage at room temperature for 1 day or in the refrigerator for up to 7 days does not clinically affect UPC. [ABSTRACT FROM AUTHOR]

Along with the study of brain activity evoked by external stimuli, the past two decades witnessed an increased interest in characterizing the spontaneous brain activity occurring during resting conditions. The identification of connectivity patterns in this so-called ''resting-state'' has been the subject of a great number of electrophysiology-based studies, using the Electro/Magneto-Encephalography (EEG/MEG) source connectivity method. However, no consensus has been reached yet regarding a unified (if possible) analysis pipeline, and several involved parameters and methods require cautious tuning. This is particularly challenging when different analytical choices induce significant discrepancies in results and drawn conclusions, thereby hindering the reproducibility of neuroimaging research. Hence, our objective in this study was to shed light on the effect of analytical variability on outcome consistency by evaluating the implications of parameters involved in the EEG source connectivity analysis on the accuracy of resting-state networks (RSNs) reconstruction. We simulated, using neural mass models, EEG data corresponding to two RSNs, namely the default mode network (DMN) and dorsal attentional network (DAN). We investigated the impact of five channel densities (19, 32, 64, 128, 256), three inverse solutions (weighted minimum norm estimate (wMNE), exact low-resolution brain electromagnetic tomography (eLORETA), and linearly constrained minimum variance (LCMV) beamforming) and four functional connectivity measures (phase-locking value (PLV), phase-lag index (PLI), and amplitude envelope correlation (AEC) with and without source leakage correction), on the correspondence between reconstructed and reference networks. We showed that, with different analytical choices related to the number of electrodes, source reconstruction algorithm, and functional connectivity measure, high variability is present in the results. More specifically, our results show that a higher number of EEG channels significantly increased the accuracy of the reconstructed networks. Additionally, our results showed significant variability in the performance of the tested inverse solutions and connectivity measures. Such methodological variability and absence of analysis standardization represent a critical issue for neuroimaging studies that should be prioritized. We believe that this work could be useful for the field of electrophysiology connectomics, by increasing awareness regarding the challenge of variability in methodological approaches and its implications on reported results.

Background: Little information is currently available about the analytical variability of urinalysis. Objective: We aimed to compare results obtained by two operators using six microscopic methods in the quantification of urinary leukocytes (WBC) and erythrocytes (RBC). Methods: Forty urine samples (10 mL) were centrifuged (450g, 5 minutes) and resuspended in 0.5 mL of supernatant. Two operators with different expertise in urinalysis interpreted sediment results using the six methods, obtained by combining the use of microscope slides (Slide) or counting chambers (Chamber) with three different techniques: bright‐field (BF) microscopy, phase‐contrast (PC) microscopy, and stained sediment (SS) evaluations. The mean WBC and RBC counts from 10 fields (Slide) or squares (Chamber) observed at 400× were used to calculate the difference and agreement between operators and methods. We also estimated the concordance between methods in classifying microhematuric or pyuric samples. Results: Operator 2 counted significantly lower WBC counts using Slide+BF (P = 0.009) and Slide+PC (P = 0.001) than Operator 1, whereas no inter‐operator differences were recorded for RBC counts. The concordance between the operators ranged from "good" to "very good." No differences or biases were found for WBC counts among the methods, and concordances were "good" to "very good"; proportional biases were found for RBC counts between Slide+BF vs Slide+SS and Slide+PC vs Slide+SS. Concordance measurements for RBC counts ranged from "good" to "very good." Conclusions: All methods yielded good reproducibility among operators, although stained SS evaluations allowed better identification of WBC by the inexperienced operator. However, we suspected that the SS preparations affected RBC counts. All other methods yielded reproducible WBC and RBC counts. [ABSTRACT FROM AUTHOR]

The performance of analytical test methods is critical to ensure decisions that affect efficacy and quality of pharmaceutical products are based on accurate and reliable results. As described in USP <1220> and advocated for in ICH Q14, continued verification of critical method attributes linked to bias and precision is essential to ensure method performance throughout the lifecycle of an analytical test method. As continued verification programs for analytical methods within the pharmaceutical industry mature, additional monitoring tools are required to deliver robust and cost-effective verification programs. Herein, a novel methodology is presented to evaluated analytical method variability directly from results generated during routine method execution. The implementation of the methodology is demonstrated for a small molecule liquid chromatographic assay method utilizing a single-point external reference calibration. Approaches to reduce the required data to be collected and broaden the applicability of the methodology to a wide range of analytical methods is described. Finally, the application of the methodology to method development activities is discussed to aid in the identification of variability sources and effectively select replication strategies, thus allowing a holistic understanding of method variability throughout the entirety of the method lifecycle. • Evaluation of analytical method variability from routine method results. • Novel methodology to estimate analytical method variability. • Evaluating analytical method variability for continuous performance verification. • Novel methodology to aid analytical method development. • Directly estimating analytical method variability from typical method results. [ABSTRACT FROM AUTHOR]

The contribution of the clinical laboratory to diagnostics is increasingly important since a great deal of clinical decisions rely on laboratory test results.

An article by Kim et al. from 2014 examined individual- and school-level variables affecting the information and communication technology (ICT) literacy level of Korean elementary school students, finding differential gender effects. In this secondary data replication, we used data from the 2018 International Computer and Information Literacy Study, focusing on data from Korea as main replication. As many characteristics of the study as possible, such as variables and analytical strategy, were modelled in the analysis. Additional analyses included 13 countries and jurisdictions, varied centring techniques for variables, and missing data treatment. The replication and analyses were pre-registered via the Open Science Framework. The main analysis did not replicate the main gender finding. However, it was also clear that, despite care taken in a rigorous replication, analytical variability still plays a large role in replications of findings, and with secondary datasets. We discuss the implications of this for secondary data replications. [ABSTRACT FROM AUTHOR]

Any large dataset can be analyzed in a number of ways, and it is possible that the use of different analysis strategies will lead to different results and conclusions. One way to assess whether the results obtained depend on the analysis strategy chosen is to employ multiple analysts and leave each of them free to follow their own approach. Here, we present consensus-based guidance for conducting and reporting such multi-analyst studies, and we discuss how broader adoption of the multi-analyst approach has the potential to strengthen the robustness of results and conclusions obtained from analyses of datasets in basic and applied research.

Background: A spray pattern (SP) test is one of the most challenging in vitro tests for nasal spray products (NSPs) associated with a high degree of variation. The total results variation observed in such studies should be in major part representative of product performance to assure high confidence when making conclusions based on obtained results. Analytical methods should be developed in a way to minimize variation contribution of random factors. A systematic statistical assessment of sources of variation is encouraged to be performed during any method development. Methods: This study includes the development of a product-shaking procedure, definition of in vivo relevant actuation parameters, and the development of a robust SP method considering NSP behavior. The final SP method is tested on different days and in different laboratories to evaluate the contribution of individual factors and interactions to the observed variance in SP using a gauge repeatability and reproducibility (GRR) model. Results: It was found that the time lag between consecutive actuations significantly influences the variability of the SP area, suggesting the importance of determining a recovery period. Factor analyst was not found to be important. Factor day was found to have the potential to impact results, mostly through interactions with other factors, suggesting that one should pay attention when performing any comparative studies within the same laboratory on different days. Significant differences were observed when the same product was tested in different laboratories. Conclusion: Key random factors, which significantly contribute to total variation, were identified using a GRR approach. By applying an appropriate control strategy over these factors, one can assure that assessed total variation can be representative of product performance. The same general approach is not only applicable to development of SP method for NSP but to all types of analytical testing as well. [ABSTRACT FROM AUTHOR]

Background and Aims: Despite the potential benefits of thromboelastography (TEG) for bedside hemostatic assessment in critical care settings, its accuracy remains to be determined, especially in critically ill neonates. We determined the intra-assay reproducibility of TEG parameters: Reaction time (R), clot kinetics (K) and Maximum Amplitude (MA) in a cohort of very low birth weight (VLBW) infants.Study Design: Observational study.Subjects: One hundred VLBW newborns.Outcome Measures: We performed TEG duplicate measurements for blood samples from VLBW newborns. To assess for correlation, we calculated the coefficients of correlation by plotting the values of the first vs the second measurement. Paired samples were compared with t-test and the coefficient of variation (CV) on paired results was also calculated as a measure of variability. To evaluate the agreement between duplicates, Bland-Altman (BA) analysis was performed.Results: We evaluated 228 TEG pairs. Both the coefficient of correlation and the BA analysis showed an acceptable level of agreement between duplicates. TEG variability (CV, mean ± SD) was highest for K (10.4%, ±12.9), lowest for MA (3.6%, ±8.0) and moderate for R (7.9%, ±9.0). The results from ANOVA one-way analysis describe different variability trends: K-CV increased at higher values, while MA-CV and R-CV increased at lower values.Conclusions: In VLBW newborns, the agreement between TEG duplicate measurements for R and MA parameters is adequate for clinical purposes. TEG is a promising tool to quickly assess hemostasis ensuring a significant blood sparing in critically ill neonates. [ABSTRACT FROM AUTHOR]

Abstract Cut point determination is an important aspect of immunogenicity assay development. The cut point can be influenced by a myriad of factors. Key among those is the analytical variability of the assay itself and biological variation due to test samples. Since a smaller cut point value may result in improved sensitivity, the existing procedures often employ statistical techniques such as outlier removal to produce a conservative cut point. Although such practices are intended to yield acceptable assay sensitivity, they may fail to fully account for biological variability in the data, thus generating higher than expected number of false positive results. In this paper, we introduce the concept of minimum cut point. It is defined as the cut point that is determined in the absence of biological variability. Under the log-normal assumption of the data used for cut point analysis, closed-form formulas are derived for the minimum cut point. This minimum cut point can be used to benchmark whether a cut point derived from a procedure can compromise assay specificity by being too low. [ABSTRACT FROM AUTHOR]

Objective: To assess whether transvaginal sonographic measurements of bladder wall thickness (BWT) have adequate reproducibility to detect differences in BWT potentially indicative of detrusor overactivity in women with overactive bladder.Study Design: Three reproducibility studies were undertaken to assess (A) total measurement error, (B) intra-observer variability and (C) inter-observer measurement in the interpretation of scans. Women recruited to the Bladder Ultrasound Study underwent a transvaginal ultrasound scan to obtain a measurement of BWT. When a second observer was available, women who agreed to have two transvaginal scans by different operators were recruited into study A. For study B the first observer reassessed a sample of the recorded images at a later date whilst for study C, a random selection of BWT images were read by a second assessor. Analytical variability, percentage of variability attributable to measurement error, within-person variation and the smallest real difference detectable were estimated.Results: One hundred and twenty-one women took part: 27 had repeat scans, 37 had scans re-read by the same observer, and 57 had scans read by two observers. In study A, 39% of the total variability in measurements was explained by measurement error (the remainder to within person change); the standard deviation (SD) of measurement error was 0.76mm and the smallest detectable clinical difference was 2.1mm. The SD of measurement error from scan interpretation was 0.42mm within observers (study B) and 0.35mm between observers (studyC).Conclusion: The high levels of measurement error for a small measurement of BWT means it is unlikely Transvaginal ultrasound measurements have insufficient reliability and reproducibility to be an accurate diagnostic test. [ABSTRACT FROM AUTHOR]

Unlike other vitamins, the vitamin D concentration in blood varies cyclically over the course of the year in relation to genetic (gender, ethnicity, polymorphisms) and environmental factors (sunlight exposure, diet, food-related or direct vitamin D supplementation, skin pigmentation). Although the major diagnostics manufacturers have recently developed improved automated 25-hydroxy vitamin D immunoassays, the intra- and interlaboratory variability is still high (especially at low vitamin D concentrations) which might lead to incorrect vitamin D deficiency/insufficiency diagnosis. Moreover, despite recent efforts to standardize the assay and minimize its variability, the current bias for measured vitamin D concentrations is often still above the desirable ± 10% criterion. Because the implications of low vitamin D concentrations in non-skeletal diseases are still partially unknown, international guideline recommendations for establishing meaningful ranges, at any time over the course of the year, irrespective not only of environmental and personal factors but also of instrumental variability, are needed. In this review, we discuss the main factors that influence the variability of vitamin D concentrations and whether a centile curve, individually calculated by a theoretical equation considering such factors, might be better suited than a fixed limit to assess abnormal vitamin D concentrations in otherwise healthy subjects. Vitamin D reference ranges during pregnancy, childhood, or diagnosed illnesses, which merit separate discussion, are beyond the scope of this review. [ABSTRACT FROM AUTHOR]

• Analytical variability and absence of consensus over analytical approaches is a critical issue in neuroimaging analyses. • Analytical variability related to the number of electrodes, source reconstruction algorithms, and functional connectivity measures in the EEG source connectivity analysis has a substantial impact on the outcomes. • A high number of electrodes (at least 64) is needed to accurately infer cortical resting-state networks from recorded scalp signals. • A very careful choice of the inverse solution/connectivity measure combination is needed since our results showed significant variability in the networks reconstructed using different inverse solutions and connectivity measures. Along with the study of brain activity evoked by external stimuli, the past two decades witnessed an increased interest in characterizing the spontaneous brain activity occurring during resting conditions. The identification of connectivity patterns in this so-called "resting-state" has been the subject of a great number of electrophysiology-based studies, using the Electro/Magneto-Encephalography (EEG/MEG) source connectivity method. However, no consensus has been reached yet regarding a unified (if possible) analysis pipeline, and several involved parameters and methods require cautious tuning. This is particularly challenging when different analytical choices induce significant discrepancies in results and drawn conclusions, thereby hindering the reproducibility of neuroimaging research. Hence, our objective in this study was to shed light on the effect of analytical variability on outcome consistency by evaluating the implications of parameters involved in the EEG source connectivity analysis on the accuracy of resting-state networks (RSNs) reconstruction. We simulated, using neural mass models, EEG data corresponding to two RSNs, namely the default mode network (DMN) and dorsal attentional network (DAN). We investigated the impact of five channel densities (19, 32, 64, 128, 256), three inverse solutions (weighted minimum norm estimate (wMNE), exact low-resolution brain electromagnetic tomography (eLORETA), and linearly constrained minimum variance (LCMV) beamforming) and four functional connectivity measures (phase-locking value (PLV), phase-lag index (PLI), and amplitude envelope correlation (AEC) with and without source leakage correction), on the correspondence between reconstructed and reference networks. We showed that, with different analytical choices related to the number of electrodes, source reconstruction algorithm, and functional connectivity measure, high variability is present in the results. More specifically, our results show that a higher number of EEG channels significantly increased the accuracy of the reconstructed networks. Additionally, our results showed significant variability in the performance of the tested inverse solutions and connectivity measures. Such methodological variability and absence of analysis standardization represent a critical issue for neuroimaging studies that should be prioritized. We believe that this work could be useful for the field of electrophysiology connectomics, by increasing awareness regarding the challenge of variability in methodological approaches and its implications on reported results. [ABSTRACT FROM AUTHOR]

Purpose: The scope of this article was to investigate the spatial and temporal variability of enantiomeric fractions (EFs) of persistent organic pollutants (POPs) in soil compared to the uncertainty of the analytical data. Materials and methods: Soil samples were taken with high spatial resolution at two sites in Czech Republic in 2008 to investigate variability on a small spatial scale. In addition, composite soil samples were taken from ten sites in 2005 and 2008 to investigate temporal variations. All samples were analysed for a suite of soil properties as well as concentrations and EFs of polychlorinated biphenyl (PCB) -95, PCB-132 and PCB-149; α-hexachlorocyclohexane (HCH); o, p′-dichlorodiphenyltrichloroethane (DDT); and o, p′-dichlorodiphenyldichloroethane (DDD). Results and discussion: Median EFs of PCB-95 and PCB-149, α-HCH, o, p′-DDT and o, p′-DDD did not change significantly on the sites sampled in 2005 and again in 2008, while PCB-132 changed from EF = 0.38 to EF = 0.53. The sampling methodology is therefore very important, and composite samples will not be the best option if enantioselective degradation processes are investigated. Non-racemic EFs of POPs in the subsampled sites in 2008 were correlated to soil parameters, such as total organic carbon (TOC), total nitrogen and humic acids. These parameters are site specific and might vary on a small scale. This can explain why certain soil parameters are reported as significantly correlated with non-racemic EFs of chiral POPs in some studies, but not always in other similar studies. Conclusions: While composite samples may still represent the overall prevailing EF range, they are not ideally suited to study enantiomeric degradation processes, which are taking place at a relative small scale, depending on the heterogeneity of soil parameters such as TOC, total organic nitrogen (TON) and humic acids. [ABSTRACT FROM AUTHOR]

Quantification of proteinuria is a fundamental step in staging dogs with chronic kidney disease and in monitoring the course of disease or the efficacy of anti-proteinuric treatments. Analytical precision and accuracy of the proteinuria assessment could be affected by several factors such as biological variability, different operators and quality control materials. The aim of this study was to assess whether inter-laboratory variability could affect the urinary protein to creatinine (UPC) ratio and whether this variability may affect patient classification according to the International Renal Interest Society (IRIS) sub-staging system. The same urine samples were analysed in three different laboratories using different instruments and different reagent brands. The results of the three laboratories were highly correlated to each other although urinary protein (UP), urinary creatinine (UC) and the UPC ratio of one laboratory were found to be significantly higher than those of the other two. No significant differences between the other two laboratories were recorded. The concordance in classifying dogs according to the IRIS guidelines was good if all three proteinuria categories were analysed separately or if borderline proteinuric (BP) dogs were included in the proteinuric group, and very good if BP dogs were merged into the non-proteinuric group. The inter-laboratory variability in UPC ratio measurement was not so great as to impede the identification of proteinuric dogs, but may influence the estimation of the magnitude of proteinuria. [ABSTRACT FROM AUTHOR]

A way of uncertainty calculation from test sample preparation in the laboratory was presented on the example of feeds. The essence of the proposal lies in separating two components of results' variability expressed as coefficient of variation CV: analytical variability CV (repeatability) and technical variability CV corresponding with the inhomogeneity of a component. The law of Gauss's error propagation was used. Analytical variability CV was calculated from the range of duplicate analyses, following Nordtest Handbook. It was assumed that the coefficient of technical variability CV is the measure of the standard uncertainty from sample preparation in the uncertainty budget of a method u, and expanded uncertainty U for k = 2 ( P = 95 %) can be easily calculated as U = 2 u. Calculated uncertainties with uncertainties from sample preparation for loose feed and no ground premixture have increased from 4 to 125 % and were higher than analytical uncertainties calculated acc. to GUM during validation of methods. In the case of granulated feed mixture, the obtained uncertainties were similar. Grinding the premix results in lower uncertainties. Uncertainty from sample preparation should be taken into account in the uncertainty budget of a test method, especially in the case of inhomogeneity of tested materials. [ABSTRACT FROM AUTHOR]

Background: This study aimed to determine the analytical imprecision of calculated neutrophil to lymphocyte (NLR) and lymphocyte to monocyte ratios generated from manual differential white blood cell (WBC) counts in peripheral blood smears, and to describe how to report the uncertainty around a single WBC ratio result. No information on the analytical imprecision of WBC ratios in dogs is available. Methods: Coefficient of variations (CVs) of paired readings of one operator on 105 smears (intraoperator variability) and of three operators on 301 smears (interoperator variability) were calculated. The interoperator agreement was examined with the Fleiss' kappa coefficient (κ). Observed total errors (TEos), expanded measurement of uncertainty (EMU) and reporting intervals (RIs) were also calculated. Results: Median CVs ranged from 3.14 to 28.28 (intraoperator) and from 5.39 to 53.85 (interoperator). No agreement among operators was found around the cut‐offs. TEos were higher than allowable total errors in 32%–88% of smears. EMU ranged from 0.10 to 1.13. According to the RI, the calculated WBC ratios should be rounded to the nearest 10. Conclusion: WBC ratios should be interpreted cautiously in dogs. The EMU should be reported to make the clinician aware of the uncertainty of these parameters. For example, an NLR result of 17 is needed to have high confidence that the result is above a cut‐off of 6. [ABSTRACT FROM AUTHOR]

Highlights: [•] Accuracy, imprecision and sensitivity of 17 estradiol assays was assessed and compared to a reference method. [•] Substantial variability in serum E2 measurements in samples from pre- and postmenopausal women and men was observed. [•] The analytical performances of most assays do not meet current needs in research and patient care. [•] Standardization can improve the observed variability across laboratories. [ABSTRACT FROM AUTHOR]

Background: A number of methods have been developed to measure small dense low-density lipoprotein cholesterol (sd-LDL-C) to evaluate atherogenic risk in the population. However, to our knowledge there are no reports about the biologic variability of these lipoproteins. Therefore, the aim of this work was to estimate sd-LDL-C biological variability, and with this information establish quality specifications, index of individuality (II) and reference change values (RCV). Methods: To estimate within- and between-subject biological variability, sd-LDL-C in serum was measured in 24 individuals (11 female and 13 male) for 5 consecutive days and then, at 2 and 3 weeks. Quality specifications, II, and RCVs were estimated according to procedures described. Results: Total within- and between-subject biological variability, expressed as coefficient of variation, was 9.1% and 20%. Meanwhile, within- and between-biological variability in female and men was 10.9% and 6.7%, and 22% and 17%, respectively. Desirable quality specification to the sd-LDL-C method was 4.6% for analytical imprecision, bias 5.5% and total allowable error of 11.4%; the II was 0.46 and the RCV (calculated at 95% and 99% of significance) was 27.1% and 35.7%, for the total data. Conclusions: Short-term biological variability components were determined, and then used to estimate quality specifications, II and RCV for sd-LDL-C precipitation assay. To our knowledge, this is one of the first reports about sd-LDL-C biological variability, so that this information can be used as a starting point to develop long-term studies of biological variability for sd-LDL-C. [ABSTRACT FROM AUTHOR]

Abstract: In support of the implementation of the Water Framework Directive (WFD, 2000/60/EC), three intercomparison exercises were carried out on European rivers (Po, Danube and Meuse) in order to assess the current state of monitoring methodologies. Laboratories from European Union (EU) Member States (MSs) were invited to gather at the selected EU river and sample together, each laboratory with its own method. Participants simultaneously sampled the river water and analyzed according to their protocols. A selection of priority substances (PSs) [i.e. polybromodiphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and alkyl phenols (APs)] included in Directive 2008/105/EC were analyzed in standard solutions, extracts from river waters and river-water samples in order to investigate variabilities in different steps of the analytical process. Concentrations measured in river samples using WFD-monitoring protocols showed that even some of the most challenging WFD PSs (e.g., PAHs, PBDEs and APs) can be measured at WFD-relevant concentrations with methods currently applied in MSs, but variability is still too great and not all laboratories meet required limits of quantification. Hindrance to the implementation of the monitoring requirements is therefore not the technical feasibility of analysis at these concentration levels, but rather communication, knowledge exchange and harmonization among the laboratories involved. [Copyright &y& Elsevier]

Abstract: The xMAP-Luminex multiplex platform for measurement of Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarkers using Innogenetics AlzBio3 immunoassay reagents that are for research use only has been shown to be an effective tool for early detection of an AD-like biomarker signature based on concentrations of CSF Aβ1–42, t-tau and p-tau181. Among the several advantages of the xMAP-Luminex platform for AD CSF biomarkers are: a wide dynamic range of ready-to-use calibrators, time savings for the simultaneous analyses of three biomarkers in one analytical run, reduction of human error, potential of reduced cost of reagents, and a modest reduction of sample volume as compared to conventional enzyme-linked immunosorbant assay (ELISA) methodology. Recent clinical studies support the use of CSF Aβ1–42, t-tau and p-tau181 measurement using the xMAP-Luminex platform for the early detection of AD pathology in cognitively normal individuals, and for prediction of progression to AD dementia in subjects with mild cognitive impairment (MCI). Studies that have shown the prediction of risk for progression to AD dementia by MCI patients provide the basis for the use of CSF Aβ1–42, t-tau and p-tau181 testing to assign risk for progression in patients enrolled in therapeutic trials. Furthermore emerging study data suggest that these pathologic changes occur in cognitively normal subjects 20 or more years before the onset of clinically detectable memory changes thus providing an objective measurement for use in the assessment of treatment effects in primary treatment trials. However, numerous previous ELISA and Luminex-based multiplex studies reported a wide range of absolute values of CSF Aβ1–42, t-tau and p-tau181 indicative of substantial inter-laboratory variability as well as varying degrees of intra-laboratory imprecision. In order to address these issues a recent inter-laboratory investigation that included a common set of CSF pool aliquots from controls as well as AD patients over a range of normal and pathological Aβ1–42, t-tau and p-tau181 values as well as agreed-on standard operating procedures (SOPs) assessed the reproducibility of the multiplex methodology and Innogenetics AlzBio3 immunoassay reagents. This study showed within-center precision values of 5% to a little more than 10% and good inter-laboratory %CV values (10–20%). There are several likely factors influencing the variability of CSF Aβ1–42, t-tau and p-tau181 measurements. In this review, we describe the pre-analytical, analytical and post-analytical sources of variability including sources inherent to kits, and describe procedures to decrease the variability. A CSF AD biomarker Quality Control program has been established and funded by the Alzheimer Association, and global efforts are underway to further define optimal pre-analytical SOPs and best practices for the methodologies available or in development including plans for production of a standard reference material that could provide for a common standard against which manufacturers of immunoassay kits would assign calibration standard values. [Copyright &y& Elsevier]

Objectives: There are no recognized analytical methods for measuring oil mist and vapours arising from drilling fluids used in offshore petroleum drilling industry. To inform the future development of improved methods of analysis for oil mist and vapours this study assessed the inter- and intra-laboratory variability in oil mist and vapour analysis. In addition, sample losses during transportation and storage were assessed. Methods: Replicate samples for oil mist and vapour were collected using the 37-mm Millipore closed cassette and charcoal tube assembly. Sampling was conducted in a simulated shale shaker room, similar to that found offshore for processing drilling fluids. Samples were analysed at two different laboratories, one in Norway and one in the UK. Oil mist samples were analysed using Fourier transform infrared spectroscopy (FTIR), while oil vapour samples were analysed by gas chromatography (GC). Results: The comparison of replicate samples showed substantial within- and between-laboratory variability in reported oil mist concentrations. The variability in oil vapour results was considerably reduced compared to oil mist, provided that a common method of calibration and quantification was adopted. The study also showed that losses can occur during transportation and storage of samples. Conclusions: There is a need to develop a harmonized method for the quantification of oil mist on filter and oil vapour on charcoal supported by a suitable proficiency testing scheme for laboratories involved in the analysis of occupational hygiene samples for the petroleum industry. The uncertainties in oil mist and vapour measurement have substantial implications in relation to compliance with occupational exposure limits and also in the reliability of any exposure–response information reported in epidemiological studies. [ABSTRACT FROM AUTHOR]

Hematologic parameters are commonly utilized in sports medicine and antidoping testing. However, there are no universally accepted methodologies for comparing the performance of automated blood analyzer systems. To address this problem, we selected and examined 19 studies from a review of literature published from 2000 to 2010. Meaningful discrepancies were found between measurements obtained with different analytical systems. Because harmonization and clear standardization of methods are lacking, the analytical variability often largely exceeds intra- and inter-individual biological differences, producing equivocal test results unreliable for clinical and antidoping testing. A central criticality to applying the Bayesian approach is analytical variability, but the use of different analytical technologies precludes the comparison of inter-methods for determining the robustness of blood variables and their clinical significance. Therefore, future multicenter studies are needed to compare analytical methodologies and blood analyzer systems, and to establish worldwide-accepted standards and quality control protocols. [ABSTRACT FROM AUTHOR]

External quality assessment (EQA) schemes are national or transnational programmes designed to control the analytical performance of clinical laboratories and to maintain inter-laboratory variability within acceptable limits. In such EQA programmes, participants are usually grouped by the type of assay technique/equipment they use. The coefficient of variation ( CV) is a simple tool for comparing the inter-laboratory reproducibility of such techniques: the lower the CV, the better the analytical performance. Serum protein electrophoresis, a laboratory test profile consisting of five fractions (albumin, α1, α2, β and γ globulins) summing up to 100% of total proteins, can also be assayed in different ways depending on the media or the analytical principle. We propose a multivariate CV for comparing the performance of electrophoretic techniques in EQA, thus extending the univariate CV concept. First, the compositional nature of electrophoretic data requires a one-to-one transformation from the five-dimensional to the four-dimensional space. Next, robust estimations of the mean and the covariance matrix are needed to avoid the effect of outliers. The new approach is illustrated on electrophoretic datasets from the French and Belgian national EQA programmes. [ABSTRACT FROM AUTHOR]

Background: The Belgian External Quality Assessment Scheme for Flow Cytometry evaluates the long-term analytical performance of participating laboratories by calculating a regression line between the target and reported values of each parameter for each laboratory during the past 3 years. This study aims to develop a method to find laboratories with aberrant variability or bias using robust techniques and to obtain robust estimates of the variability. Methods: A method is proposed to find outliers with respect to the individual regression line, followed by a step to find regression lines with excessive variability and finally a step to find regression lines with high bias. Results: The model was applied to the results obtained by 52 laboratories for CD4%. From the 1340 data points, 35 were determined to be regression outliers. The second step revealed one regression line with excessive variability; the third step detected three regression lines with exceeding bias. Conclusions: The methodology allows assessment of the long-term performance of laboratories, taking into account samples with different target values. Outliers in the first step indicate accidental mistakes, outliers in the second and third step point to high analytical variability or bias. Clin Chem Lab Med 2010;48:645–50. [ABSTRACT FROM AUTHOR]

Abstract: Background: Though mass spectrometry (MS) assays are increasingly used for routine clinical measurements of serum total testosterone (TT), information about the variability of results is limited. This study assessed the variability of TT measurement results from routine MS assays. Methods: Twenty serum samples (12 females, 8 males) were analyzed on 2 days by seven high performance liquid chromatography (HPLC), and one gas chromatography (GC)–tandem mass spectrometry (HPLC–MS/MS, GC–MS/MS) assays. Two samples (male and female) were provided in five replicates to assess the within-run variability. Results were compared against those obtained at National Institute of Standards and Technology (NIST). The within- and between-laboratory variability was assessed for each sample. Comparisons to the NIST results were performed using bias plot and Deming regression analysis. Results: The overall coefficient of variation of the results obtained with MS assays was <15%CV at >1.53nmol/L and <34%CV at 0.3nmol/L. The between-assay variability was the major contributor to the overall variability. The assay precision was the highest (<3%CV) with assays using liquid–liquid extraction for sample preparation or GC–MS/MS. The mean percent difference to the reference assay was 11%. The slopes of Deming regression analysis of the MS assays were between 0.903 and 1.138 (correlation coefficient: >0.996). TT concentrations for one assay were above the measurement range. Conclusions: The variability of TT measurement results among MS assays is substantially smaller than that reported for immunoassays. The type of sample preparation may affect assay precision. Standardizing assays can further reduce the variability of measurement results. [Copyright &y& Elsevier]

Recent national concerns regarding the environmental occurrence of emerging contaminants (ECs) have catalyzed a series of recent studies. Many ECs are released into the environment through discharges from wastewater treatment plants (WWTPs) and other sources. In 2005, the U.S. Geological Survey and the City of Longmont initiated an investigation of selected ECs in a 13.8-km reach of St. Vrain Creek, Colorado. Seven sites were sampled for ECs following a Lagrangian design; sites were located upstream, downstream, and in the outfall of the Longmont WWTP, and at the mouths of two tributaries, Left Hand Creek and Boulder Creek (which is influenced by multiple WWTP outfalls). Samples for 61 ECs in 16 chemical use categories were analyzed and 36 were detected in one or more samples. Of these, 16 have known or suspected endocrine-disrupting potential. At and downstream from the WWTP outfall, detergent metabolites, fire retardants, and steroids were detected at the highest concentrations, which commonly exceeded 1 μg/l in 2005 and 2 μg/l in 2006. Most individual ECs were measured at concentrations less than 2 μg/l. The results indicate that outfalls from WWTPs are the largest but may not be the sole source of ECs in St. Vrain Creek. In 2005, high discharge was associated with fewer EC detections, lower total EC concentrations, and smaller EC loads in St. Vrain Creek and its tributaries as compared with 2006. EC behavior differed by individual compound, and some differences between sites could be attributed to analytical variability or to other factors such as physical or chemical characteristics or distance from contributing sources. Loads of some ECs, such as diethoxynonylphenol, accumulated or attenuated depending on location, discharge, and distance downstream from the WWTP, whereas others, such as bisphenol A, were largely conservative. The extent to which ECs in St. Vrain Creek affect native fish species and macroinvertebrate communities is unknown, but recent studies have shown that fish respond to very low concentrations of ECs, and further study on the fate and transport of these contaminants in the aquatic environment is warranted. [ABSTRACT FROM AUTHOR]

A method transfer study is designed to successfully transfer technology from an origination laboratory to a destination laboratory. Following quality by design principles, a method transfer study is part of an analytical process to confirm the repeatability and ruggedness of the technology to be transferred. The primary objective of the study and statistical analysis is to demonstrate equivalence between laboratory mean responses. Additional information demonstrating the consistency of analysts within laboratories and the proficiency of each laboratory and analyst to reproduce the expected result can be obtained. Three representative study designs are discussed and an example is presented. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: : To evaluate the inter-laboratory reproducibility of blood test for liver fibrosis: FibroMeter, Fibrotest, APRI and their composites variables. Design and methods: : Four studies, including 147 patients, were performed: study #1 included 2 metachronous blood samples and 2 laboratories; studies #2, #3 and #4 included synchronous samples with assays delayed at day 1 in 12 laboratories, at day 0 in 10 laboratories and at day 0 or 1 in 2 laboratories, respectively. Agreement was evaluated by the intraclass correlation coefficient (r ic). Results: : In studies #1, #2 and #4, r ic for FibroMeter was 0.893, 0.942 and 0.991, respectively. In study #3, the r ic were: FibroMeter: 0.963, Fibrotest: 0.984, APRI: 0.949. Large simulated variations in composite variables had a weak impact on FibroMeter. Conclusions: : When blood marker limits are controlled, inter-laboratory agreement of blood tests is excellent in clinical practice conditions. Blood tests are robust against the variability of composite blood variables. [Copyright &y& Elsevier]

Background: ISO 15189: 2003 was developed in order to establish requirements for the Accreditation of Clinical Laboratory Quality Management System and Technical Competition, including standards from the pre to post examination stages. From the medical point of view the most important issue of the new norm, is the need to generate medically relevant results, making necessary for the laboratory professionals to watch for the reliability of the studies, and to become more involved on the suitable indication and utilization of the tests, and to be aware on the correct interpretation and better use of the results. Objective: To review ISO 15189: 2003 and to document the medical relevance concept and the issues that may derive from the human perspective and from the technological dimension. Material and methods: This is a revision article on which the analytical process in its three stages is evaluated. Practical definitions, formulas and examples are presented as indicators of medical relevance that can be applied on the internal and external quality control programs. Results: The basic utility of the tests of the laboratory depends fundamentally on their medical relevance, which can as be evaluated on an objective form in the internal quality programs and in the external proficiency schemes. Discussion: Medical relevance depends from the start on the decision to use the clinical laboratory tests, depending on what test is to be performed, who indicates it, why and what for is carried out, who process it and where is developed, who controls it and finally what is done with the results. When the tests are carried out under suitable conditions, in a laboratory with well established quality control programs in which objective indicators are applied, it turns out feasible to evaluate the relevance of the results through the simultaneous measurement of the biological variability and analytical variability according to the described method on this communication. [ABSTRACT FROM AUTHOR]

Background: SIX SIGMA appeared in the industry in 1979 in order to obtain quality improvement manufacture processes to a level of 3.4 defects per million units (DPMU). It involves all the system from agreed goals establishment with customer's requirements, to statistical data measurement, team work, and continuous quality improvement. Objective: To briefly review and document SIX SIGMA principles and tools in order to evaluate its applicability on the clinical laboratory, including the importance of comparing the impact of SIX SIGMA level with pre-established analytical goals according to the analytical coefficient of variation of Tonks and Aspen that have been used in clinical laboratories for decades as precision indicators. Material and methods: This is a revision of the basic concepts and the fundamental methods of SIX SIGMA, including definitions, formulas and practical exercises and examples on the indicators of analytical variability based on pre-established reference limits and ranks of biological variability for the analytical control of quality according to Tonks, Aspen and SIX SIGMA criteria, emphasizing the applicability of the relative coefficient of variation CVR as practical tool for analytical goal management on any laboratory test. Results: The criterion of Tonks is equivalent to 25.0% of the normal rank representing a biological standard deviation. The Aspen criterion is equivalent to 50% of Tonks level representing 12.5% of the normal rank. In order to reach SIX SIGMA level it is necessary to improve Tonks level precision in six times, which implies to reduce the analytical variability to 4.2% of biological variability. In order to evaluate the relation that exists between biological variability (BV) and the analytical variability (AV) it is recommended to calculate quotient AV / BV which will give a result of < 1.0 according to Tonks, < 0.50 according to Aspen and <0.17 when SIX SIGMA level is reached. Discussion: The establishment of attainable and challenging analytical goals is the first step in any quality control system. The relative coefficient of variation calculation allows laboratories a reliable and easy approach on analytical goal establishment for any analyte with the only condition of having suitable reference limits for the attended population and the calculation of the analytical coefficient of variation for the specific test. The advance in quality improvement depends on the establishment of the actual level in which the laboratory is at the present moment. In order to improve quality it is necessary to improve good laboratory practices and to elevate the automation level of the laboratory. The achievement of analytical goals will be different depending on the level in which they are applied in such a way that the results that are obtained in the Internal Program of Control of Quality should be better than those than are reached on External Evaluation Quality Schemes, because for statistical reasons the confidence intervals vary inversely depending on the number of variables that take part in the process. [ABSTRACT FROM AUTHOR]

Background: ISO 15189 «Quality Management in the Medical Laboratory» has been developed for clinical laboratories evaluation, quality improvement and accreditation. This standard involves analytical process completely, from pre to post examination stage, giving importance to biological and analytical variability in addition to methodological traceability, test validation and the measurement of uncertainty and medical relevance. Objective: To clearly and briefly review and document uncertainty biostatistical principles that are applicable to the clinical laboratory including standard error, relative coefficient of variation, standard deviation index and total error as fundamental indicators of quality control. Material and methods: This is a review article of the scientific literature in which definitions, formulas and practical exercises on uncertainty indicators and total variability in analytical control of quality are documented. Results: It is clearly demonstrated that the utility of laboratory tests depend on multiple factors, which must be known, supervised and controlled as far as possible through analytical process. Discussion: The utility of these concepts depends on the routine application of quality indicators, which at the present time is highly feasible, since personal computers are already common tools in almost every clinical laboratory worldwide. Daily estimation of these formulas is actually quite simple leading to a dramatic positive impact on quality improvement of laboratory data when knowledge can be applied in order to control uncertainty. [ABSTRACT FROM AUTHOR]

Abstract: A multi-company investigation is presented to obtain and compare precision results for LC assay procedures. Forty-four drug substances and drug products of various types subjected to 156 stability studies, with 2915 assay values in total, were included. This provides an excellent source of real long-term precision estimates, as the same analytical procedure was applied during the whole stability study, extending from 12 to 60 months. Intermediate precision was calculated either using the residual standard deviation of the regression line or applying an analysis of variances, depending on whether there was a significant degradation of the analyte or not. The results show impressively the large intervals where the individually calculated parameters scatter. Distribution ranges and averages for repeatability, intermediate precision, and the ratio between the two precision levels are mainly dependent on the type of drug product. Repeatabilities were found up to 0.8% for solutions, 1.6% for drug substances, 1.9% for tablets, 2.3% for creams, and 3.4% for a bath. For intermediate precision, which includes additional variability factors due to the reference standard, operator, equipment, reagents, etc., a similar dependency was obtained with a slightly changed order: up to 1.1% for drug substances, 2.2% for solutions, 2.3% for tablets, 3.1% for creams, and 3.2% for a bath. The ratio between the precision levels is up to 2.5 and similar for all investigated drug product types, apart from solutions with up to 5.3. These differences for the types of drug product may be explained by the influence of the sample and/or the sample preparation: the more complex, the higher the variability contribution. For the investigated examples, the impact of the analyte and of the concentration (dosage) seems to be of less importance. Therefore, a classification of drug product types for orientation on acceptable precision (ranges) for LC assay seems to be possible. [Copyright &y& Elsevier]