How to deal with semi-quantitative tests? Application of an ordinal scale model to measurements of urine glucose.
ABSTRACT The interpretation of semi-quantitative methods has always been difficult, because the different kitmanufacturers use varying concentration values and there is a considerable overlap between kit-defined concentrations within the same kit (Kit: 'Ready-to-use' measuring system specific for each manufacturer's product).
More than 2000 private practitioners and laboratories participated in three external quality control surveys on urine-glucose performed with a total of six control materials with known concentrations.
The ordinal scale model for evaluation of dichotomous methods based on rankit transformation of fractions of positive results (Petersen et al. Scand J Clin Lab Invest 2008;68:298-311) has been extended and modified to handle semi-quantitative data. Here, the percentages of results larger than the kit-concentration is calculated for each control sample and applied as a dichotomous method. Thereafter, these percentages are separated into all the defined kit-concentrations.
A total of eight kits had more than 50 measurements on at least four control materials which made them eligible for the calculations of logarithmic mean and standard deviation and thereby geometric mean and coefficient of variation for each of the kit-concentrations of each kit. Based on these parameters, the true concentration for selected percentages of each kit-concentration could be estimated. Moreover, the percentages of the different kit-concentrations could be calculated for each known true concentration.
The present model is a powerful tool for improved characterization of semi-quantitative kits, which makes it possible to evaluate and validate kits and to optimize external quality control.
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ABSTRACT: In April of 2011, Bio-Rad Laboratories Quality System Division (Irvine, CA, USA) hosted its third annual convocation of experts on laboratory quality in the city of Salzburg, Austria. As in the past 2 years, over 60 experts from across Europe, Israel, USA and South Africa convened to discuss contemporary issues and topics of importance to the clinical laboratory. This year's conference had EN/ISO 15189 and accreditation as the common thread for most discussions, with topics ranging from how to meet requirements like uncertainty to knowledge gained from those already accredited. The participants were divided into fi ve discussion working groups (WG) with assigned topics. The outcome of these discussions is the subject of this summary.Clinical Chemistry and Laboratory Medicine 09/2012; 50(9):1547-58. DOI:10.1515/cclm-2012-0003 · 2.96 Impact Factor
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ABSTRACT: The setting of analytical quality specifications in laboratory medicine has attracted attention for many years. Over time, many strategies were advocated and all had advantages and disadvantages. In the final decade of the last millennium, considerable confusion existed on how to define analytical quality specifications correctly and how to apply them in everyday practice. This led to wide professional interest. In 1999, a consensus conference sponsored by IUPAC, IFCC and WHO was held in Stockholm on “Strategies to Set Global Analytical Quality Specifications in Laboratory Medicine”. The consensus set useful and well-documented strategies for the setting of analytical quality specifications into a hierarchy with the best strategy at the highest level, namely, (1) Evaluation of the effect of analytical performance on clinical outcomes in specific clinical situations, (2) Evaluation of the effect of analytical performance on clinical decisions in general, (3) Published professional recommendations, (4) Performance goals set by regulatory bodies and EQAS organisers, and (5) Goals based on the current state of the art. Much success has been achieved since the promulgation of the statement with the approach being adopted by many in laboratory medicine for a very wide variety of purposes, particularly in quality management. However, there is a requirement for additional investigation of, inter alia, quality specifications for examinations done on measurements performed on ordinal and nominal scales, pre-analytical factors and matrix effects, examinations done as POCT, target values of control materials, and ways in which analytical quality specifications can be used both to set what is the optimum performance and as a tool for assessment of everyday practice. KeywordsAnalytical bias and imprecision-Analytical goals-Analytical requirements-Laboratory medicine-Matrix effects-Point-of-care-testingAccreditation and Quality Assurance 06/2010; 15(6):323-330. DOI:10.1007/s00769-009-0630-8 · 1.05 Impact Factor
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ABSTRACT: As a part of a series of yearly meeting, in May 2010 over 40 medical laboratory opinion leaders, pathologists, clinical biochemists and physicians from Europe, Israel and South Africa gathered together in Bardolino, Italy to discuss issues and current challenges for laboratory medicine, including a) the use of biological variation 10 years after the Stockholm Conference; b) achieving quality in point-of-care testing; c) assessing risk and controlling sources of error in the laboratory; d) determining the appropriate frequency of quality control; and f) putting laboratory medicine at the core of patient care. The intended goal of the convocation was to give laboratory professionals from different countries and backgrounds the opportunity to share ideas, concerns and experiences in previously mentioned areas of interest. This paper provide a synopsis of the reports from each working group.Clinical Chemistry and Laboratory Medicine 03/2011; 49(5):793-802. DOI:10.1515/CCLM.2011.149 · 2.96 Impact Factor