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92 Int J Med Biochem BV is defined as the random fluctuations of an analyte concentration around a homeostatic set point in an individual [3]. The application of BV data in the clinical laboratory is very comprehensive and valuable. The components of BV can be used to determine the timing and frequency of sampling in the pre-pre-analytical and pre-analytical phases; quality specifications, such as imprecision, bias, and total error in the analytical phase; and population-based reference intervals, individuality index, and reference change values in the post-analytical and post-post-analytical phases; they are very important during the interpretation and evaluation of test results [2, 4]. The aim of the present study was to determine whether thirdparty control data of 26 clinical biochemistry parameters collected over a period of 6 months would meet BV-based analytical quality specifications (minimum, desirable, and optimum). For this purpose, we decided to use third-party control samples independent of the manufacturers of the devices and reagents present in our laboratory. We procured control samples sufficient for a 1-year period. These samples met the required conditions in terms of stability and analyte concentration at clinical decision level, and so on. We used these control samples for internal quality control in our laboratory, and the results were evaluated by the Unity Real Time® program, which was used to compare results on an international scale, and the Westgard AdvisorTM software, which was an integral part of the program. Using the Unity Real Time® program, the mean, standard deviation, and coefficient of variation (CV) values were calculated for the measurands evaluated using the internal quality assurance program. Bias is defined as “the systematic deviation in the test results indicating the difference between the mean of the serial replicate measurements and the expected true value or the value that is accepted as true” [5]. The programs mentioned above enable us to compare our mean values as calculated for each test using peer-group means, which we accepted as the true value. Unlike the external quality assessment programs, in which a single measurement result is compared with the peer-group mean, these programs allowed us to detect our actual bias. We investigated whether the CV and bias values of each test and the total analytical error (TAE) derived from these values were within the CV, bias, and total allowable error (TEa) limits that are required by each of the three quality specifications of BV (minimum, desirable, and optimum), and also, which BV quality specification was more appropriate for use in our laboratory. Materials and Methods In the present study, test performances in Gaziosmanpasa Taksim Education and Research Hospital's Biochemistry Laboratory were evaluated according to the BV acceptance criteria (minimum, desirable, and optimum) as updated by Ricos and colleagues [6]. Furthermore, the quality specifications of BV that could be met by the performance of routinely analyzed biochemical tests were identified. The study was conducted over a 6-month period from February 3 to August 3, 2016 using a Beckman Coulter AU5800 clinical chemistry analyzer. The study duration and the method to be used in data evaluation were both determined according to the Clinical Laboratory and Standards Institute (CLSI) C24-A3 guideline, which states that the mean, standard deviation, and control limits should be determined based on the cumulative data obtained over a period of 3 to 6 months [7]. During the study period, the preliminary data were collected over 20 working days in 1 month, with 40 measurements made for each level, and these data were used to calculate the preliminary mean and standard deviation values (Biorad Lypocheck Clinical Chemistry Control Level 1; lot no: 14461) and Level 2; lot no: 14462). The cumulative mean and standard deviation values were calculated by adding the new data to the initial values. Cumulative control limits are known to be a better indicator of long-term test performance [8]. For each test, the control rules and control measurement numbers were determined using the Westgard Advisor software according to the analytical CV and bias values of the tests. The Unity Real Time® software was set to detect control violations automatically. Thus, the control numbers and rules were applied during the process. The detected rule violations were subjected to the necessary intervention, and the interventions Table 1. Test and methods in our laboratory Test Name Test Unit Method Albumin g/dL Colorimetric BCG ALT IU/L IFCC (and/or PLP Activation) ALP IU/L IFCC AMP Buffer Amylase IU/L CNP-Trioside CNPG3 AST IU/L IFCC (and/or PLP Activation) Direct Bilirubin mg/dL Colorimetric Diazo method Total Bilirubin mg/dL Colorimetric Diazo method Chlorid mEq/L ISE indirect Calcium mg/dL Colorimetric Arsenoza III HDL-Cholesterol mg/dL Enzymatic immunoinhibition Total Cholesterol mg/dL CHO-POD Creatinine kinase IU/L Modified IFCC method Creatinine mg/dL Modified Jaffe’s Kinetic GGT IU/L G-Glutamyl carboxy nitroanylide Glucose mg/dL Hexokinase Ferritin μg/dl Colorimetric TPTZ LDH IU/L LDH (L-P) IFCC Lipase IU/L Enzymatic 1.2-diglyceride Magnesium mEq/L Xylidyl blue Potassium mEq/L ISE indirect Phosphor mg/dL Phosphomolybdate Total proteine g/dL Biuret LDL-Cholesterol mg/dL Enzymatic immunoinhibition Sodium mEq/L ISE indirect Triglyceride mg/dL GPO-POD Uric acid mg/dL Uricase 93 Cakmak, Evaluation of analytical performance with BV criteria / doi: 10.14744/ijmb.2018.39974 were recorded. Percentage bias (%B), percentage CV (%CV), and TAE were calculated for 26 tests. We followed the policy that we established as the target for the Clinical Laboratory Improvement Amendments (CLIA) criteria for these tests in our laboratory and then made comparisons with the BV acceptance criteria. During the 6-month study period, performance reports of all tests were obtained separately according to CLIA and BV. Examined tests and assay methods All examined tests were analyzed using a Beckman Coulter AU5800 analyzer throughout the 6-month study period in accordance with the planned control procedure. The evaluation comprised 26 tests all analyzed using the routine clinical chemistry analyzer. Table 1 shows these tests, their units, and the assay methods. Quality control procedure As shown in Fig. 1, TEa for each test was determined according to BV specifications using the software program. The Westgard AdvisorTM module, which was pre-defined in the program, the calculated %B, %CV, ΔSE (critical systematic error), and sigma (σ) values for the desired parameters for a given time interval. Based on these data, the program automatically calculated the required control rule and control measurement number at the analytical quality assurance percentage, providing the best test performance according to the most appropriate error detection (Ped; probability of error detection) and false rejection (Pfr; probability of false rejection) values with the help of both OPSpecs and critical error graphics. Allowable error values based on BV specifications Table 2 shows the %TEa, %B, and %CV limits of the examined tests according to BV minimum, desirable, and optimum specifications. All %TEa, %B, and %CV values for the desired specifications were derived from the BV data. For minimum and optimum specifications, the %TEa, %B, and %CV limit values for the tests that did not have a specified value in the data were calculated using the formula given below [6]: For minimum specification: %CV<0.75CVw %B<0.375 (CVw +CVb 2)1/2 %TEa<0.375 (CVw +CVb 2)1/2+1.65 (0.75CVw) For optimum specification: %CV<0.25CVw %B<0.125 (CVw +CVb 2)1/2 %TEa<0.125 (CVw +CVb 2)1/2+1.65 (0.25CVw) where: %TEa: total allowable error; a quality requirement for a given test, %B: deviation from the true value, %CV: imprecision observed for a given method, CVw: intra-individual biological variation, CVb: inter-individual biological variation, 1.65: coefficient for 95% confidence interval. For all tests, TAE, %CV, and %B were calculated, and the BV acceptance criteria (minimum, desirable, and optimum) were used for comparison. TAE for each level of each test was calculated using the TAE=%B+1.65×CV formula in the Excel program. The %B value was accepted as its absolute value. 1.65 is the coefficient used for 95% confidence interval. The performance reports include the observed %B, the %CV values for the given level, and the recommended control rule and numbers based on the BV minimum, desirable, and optimum acceptance criteria.

international journal of medical biochemistry/international journal of medical biochemistry  :

Evaluation of analytical performance specifications of routine clinical biochemistry tests with biological variation-based total allowable error (TEa) criteria