Evaluation of biochemical methods performance in clinical laboratories: is this performance suitable for clinical application?

Background: Clinical application of the test results are profoundly influenced by laboratory errors. Nowadays, the best way to evaluate the performance of a method is to determine its sigma scale according to total allowable error (TEa) and analytical errors, including random and systematic errors. In this study, the performance of the measuring kits for biochemical analytes belonging to Pars Azmoon Company, as the most commonly used kits in Iran, was evaluated by determining their deviation index (DI) and sigma scale. Materials and methods: During the years 2013-17 and the 15th to 28th runs of the external quality assessment program (EQAP), commercial control materials were sent to about 2000 participating laboratories in each period. Based on the results of measuring the biochemical analytes by these laboratories, method performance of measuring methods was determined according to DI and sigma scale. For determining sigma scale, two different TEa was used. Results: Based on the TEa introduced by the reference health laboratory of Iran, among the 21 analyzed analytes, DI of the 7, 11, and 3 analytes were acceptable (DI up to 2.0) for 100%, 90% and less than 90% of the reported results, respectively. In sigma scale evaluation of these methods according to TEa of reference health laboratory of Iran and CLIA (Clinical Laboratory Improvement Amendments), 13 and 12 measuring methods were acceptable (sigma of at least 2.0), respectively. Conclusion: Due to the importance of the test results in medical decision making, it is necessary to improve the performance of measuring methods.