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Interlaboratory Variation (interlaboratory + variation)
Selected AbstractsInterlaboratory Comparison of Cytomegalovirus Viral Load AssaysAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2009X. L. Pang To assess interlaboratory variability in qualitative and quantitative cytomegalovirus (CMV) viral load (VL) testing, we distributed a panel of samples to 33 laboratories in the USA, Canada and Europe who performed testing using commercial reagents (n = 17) or laboratory-developed assays (n = 18). The panel included two negatives, seven samples constructed from purified CMV nucleocapsids in plasma (2.0,6.0 log10 copies/mL) and three clinical plasma samples. Interlaboratory variation was observed in both actual (range, 2.0,4.0 log10 copies/mL) and self-reported lower limits of detection (range, 1.0,4.0 log10 copies/mL). Variation observed in reported results for individual samples ranged from 2.0 log10 (minimum) to 4.3 log10 (maximum). Variation was greatest at low VLs. Assuming ± 0.5 log10 relative to the expected result represents an acceptable result, 57.6% of results fell within this range. Use of commercially available reagents and procedures was associated with less variability compared with laboratory-developed assays. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). The significant interlaboratory variability in CMV VL observed may be impacting patient care and limiting interinstitutional comparisons. The creation of an international reference standard for CMV VL assay calibration would be an important step in quality improvement of this laboratory tool. [source] Impact of the international program for quality assessment and standardization for immunological measures relevant to HIV/AIDS: QASICYTOMETRY, Issue 2 2002Francis Mandy Abstract Measurements of CD4 T-cell levels are essential for the assessment of human immunodeficiency virus (HIV) disease course, clinical staging, epidemiological studies, and decisions regarding prophylactic therapies against opportunistic infection. Until now, only in the industrialized countries was T-cell subset monitoring considered a practical option to assess disease progression. The Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS (QASI) program was established in 1997 to meet performance assessment for immunophenotyping laboratories in countries where such service is not available. The QASI program is provided at no cost to any laboratory in a resource-poor setting that wishes to participate. This report describes the beneficial impact of participation in the QASI program. Carefully selected commercial stabilized whole blood preparations were sent regularly to participating laboratories. Participants reported the T-cell subset values they obtained by flow cytometry. Once the aggregate mean values for the T-cell subsets were established for the shipment, a comprehensive and confidential report was sent to each laboratory. The results from five consecutive shipments were analyzed. The coefficient of variation decreased from 7.2% to 4.7% and from 14.2% to 8.8% for percent and absolute CD4 T-cell counts, respectively. With the implementation of the QASI program using commercial stabilized whole blood specimens, it is possible to reduce interlaboratory error. This study illustrates that a quality assessment program can improve the overall performance of laboratories. Reducing interlaboratory variation can enhance significantly the effectiveness of multicenter HIV vaccine or drug trial evaluation. Cytometry (Clin. Cytometry) 50:111,116, 2002. © 2002 Wiley-Liss, Inc. [source] The Reliability of Echocardiographic Left Ventricular Wall Motion Index to Identify High-Risk Patients for Multicenter StudiesECHOCARDIOGRAPHY, Issue 1 2006Gunnar H. Gislason M.D. Objective: To study whether the use of echocardiographic left ventricular (LV) wall motion index (WMI) is a dependable parameter for identifying patients with LV dysfunction to be enrolled in multicenter trials. Methods: Videotaped echocardiographic examinations from 200 randomly selected patients that were screened for inclusion into the DIAMOND-CHF and DIAMOND-MI trials were reevaluated by an external expert echocardiographer. WMI was calculated using the 16-segment LV model. Results: The external echocardiographer systematically found lower values of WMI than the core laboratory. The average difference in WMI was 0.18 (SD: 0.33) in the DIAMOND-CHF trial and 0.09 (SD: 0.33) in the DIAMOND-MI trial. The difference in WMI exceeded 0.33 in 34% of the patients in both trials. The cutoff value for inclusion into the DIAMOND trials was WMI , 1.2. There was an agreement on WMI dichotomized to below or above 1.2 in 82% of the patients in both trials ( , coefficient 0.66 for the DIAMOND-CHF and 0.55 for the DIAMOND-MI). Conclusions: Despite substantial interlaboratory variation in WMI in individual patients and a systematic lower WMI score by the external echocardiographer there was an acceptable overall agreement for identifying patients with severe impairment of LV function. This not only underscores the value of LV-WMI as a useful tool for selecting high-risk patients to be included in multicenter studies but also serves to warn against the use of rigid cutoff values for WMI in the treatment of individual patients. [source] Summary findings of the fourth international radiocarbon intercomparison (FIRI)(1998,2001)JOURNAL OF QUATERNARY SCIENCE, Issue 7 2002Elisabetta Boaretto Abstract Interlaboratory comparisons have been widely used in applied radiocarbon science. These are an important part of ongoing quality assurance (QA) programmes, which are vital to the appropriate interpretation of the evidence provided by the 14C record in Quaternary applications (including climate change and environmental reconstruction). International comparisons of laboratory performance are an essential component of the quality assurance process in radiocarbon dating. If the user community is to have confidence in radiocarbon results, it needs to be assured that laboratories world wide are producing measurements that are reliable and in accordance with ,good practice'. The findings from the most recent (completed in 2001) and extensive (more than 90 participating laboratories) radiocarbon intercomparison (FIRI) are reported here. This study was designed (i) to assess comparability, or otherwise, of the results from different laboratories and (ii) to quantify the extent and possible causes of any interlaboratory variation. The results demonstrate that there are no significant differences amongst the main measurement techniques (gas proportional counting, liquid scintillation counting and accelerator mass spectrometry (AMS)) but there is evidence of small laboratory offsets relative to known age samples for some laboratories. There is also evidence in some cases of underestimation of measurement precision. Approximately 10% of all results were classified as extreme (outliers) and these results were generated by 14% of the laboratories. Overall, the evidence supports the fact that radiocarbon laboratories are generally accurate and precise but that, notwithstanding internal QA procedures, some problems still occur, which can best be detected by participation in independent intercomparisons such as FIRI, where the results allow individual laboratories to assess their performance and to take remedial measures where necessary. The results from FIRI are significant in that they show a broad measure of agreement between measurements made in different laboratories on a wide range of materials and they also demonstrate no statistically significant difference between measurements made by radiometric or AMS techniques. Copyright © 2002 John Wiley & Sons, Ltd. [source] Interlaboratory Comparison of Epstein-Barr Virus Viral Load AssaysAMERICAN JOURNAL OF TRANSPLANTATION, Issue 2 2009J. K. Preiksaitis To assess interlaboratory variability in qualitative and quantitative Epstein-Barr virus (EBV) viral load (VL) testing, we distributed a panel of samples to 28 laboratories in the USA, Canada and Europe who performed testing using commercially available reagents (n = 12) or laboratory-developed assays (n = 18). The panel included two negatives, seven constructed samples using Namalwa and Molt-3 cell lines diluted in plasma (1.30,5.30 log10 copies/mL) and three clinical plasma samples. Significant interlaboratory variation was observed for both actual (range 1.30,4.30 log10 copies/mL) and self-reported (range, 1.70,3.30 log10 copies/mL) lower limits of detection. The variation observed in reported results on individual samples ranged from 2.28 log10 (minimum) to 4.14 log10 (maximum). Variation was independent of dynamic range and use of commercial versus laboratory-developed assays. Overall, only 47.0% of all results fell within acceptable standards of variation: defined as the expected result ± 0.50 log10. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). Kinetics of change in VL appears more relevant than absolute values and clinicians should understand the uncertainty associated with absolute VL values at their institutions. The creation of an international reference standard for EBV VL assay calibration would be an initial important step in quality improvement of this laboratory tool. [source] | ||||||||||