Performance verification of laboratory-developed clinical chemistry system-Analytical measurement range and clinical reportable range

Abstract

Objective To estimate the methodology for evaluating the analytical measurement range (AMR) and the clinically reportable range (CRR) in lab-developed system in clinical chemistry. Methods Method evaluation.Take serum CK for instance, a series of samples were prepared from both a specimen with a high concentration of the analyte of interest and a specimen with a low concentration for the following assays.Average slope method, linear dilution recovery method and the method recommended by Clinical and Laboratory Standards Institute (CLSI) EP6-A were used to established AMR in the lab-developed clinical chemistry system. Based on the maximum valid dilution of the specimen and the results of AMR, CRR were determined. One-half of the total error allowance (TEa) of Chinese health standard was set up as allowance error (7.5%). Results X-Y scatter plot was made by assigning sample numbers to the horizontal axis and actual measured values to the vertical axis, which determined the upper limit of AMR was approximate 1 651 U/L. The results analyzed by average slope method indicated that the linear correlation between expected values and actual measured values was determined, the correlation (r), the intercept (a) and the slope (b) met the linear standard, and AMR was 5-1 699 U/L. The results analyzed by EP6-A indicated that the best fitting curve was obtained by using cubic polynomial method, and the linearity deviation of the minimum concentration was -77.1%, which exceeded one-half of TEa. Followed by the deletion of the maximum concentration, the resumed experiment was done. The results showed that the nonlinear coefficient c of quadratic polynomial and the nonlinear coefficient c and d of cubic polynomial have no significant difference to 0, and AMR was 7.5-1 458.0 U/L. By linear dilution recovery method, the linear correlation between expected values and actual measured values was determined, the correlation (r), the intercept (a) and the slope (b) met the linear standard, the recovery rates was between 100.0% and 104.8%, and AMR is 5-1 699 U/L. The CRR was determined to be 5-33 880 U/L, which met the standard of TEa. Conclusions Average slope method, linear dilution recovery method and EP6-A method were all used to established AMR in lab-developed clinical chemistry system. Without complicated statistical analysis, linear dilution recovery method was suitable for clinical use. The linearity deviation of the minimum concentration analyzed by EP6-A did not meet the standard of the quality objective system, suggesting defects in the statistical analysis of the results.CRR was feasibly determined by using linear dilution recovery method align with AMR.(Chin J Lab Med, 2016, 39: 946-952) Key words: Creatine kinase; Clinical chemistry tests; Evaluation studies