Aim: Six Sigma methodology used in clinical laboratories is a quality management tool based on statistical calculations, focusing on process variables and providing information about process performance. In this study, we aimed to evaluate the analytical process performances of the most commonly used biochemistry and immunoassay tests in our laboratory using six sigma methodology and to measure the quality goal index of low-performing parameters.

Materials and Methods: Sigma values of 47 test parameters, including 24 biochemistry and 23 immunoassays, which are most frequently performed in routine biochemistry, were calculated using the Roche Cobas 8000 autoanalyzer in the Central Laboratory of Kayseri City Education and Research Hospital. External quality control data for December 2022 for percentage bias, 2 levels of internal quality control data as %CV1-%CV2 for %CV values, values determined by CLIA 2019 and RiliBAK for TEa rates were used.

Results: While sigma values were <3 in at least one level of sodium and chlorine tests, sigma values were ≥6 in ALP, AST, CK, creatinine, GGT, HDL, iron, LDH, magnesium, phosphorus, total protein, triglyceride, urea and uric acid tests. Among immunoassay parameters, sigma values at one level of DHEA-S test were <3, while sigma values at one level of AFP, CA15-3, CA125, CEA, CA19-9, free PSA, total PSA, ferritin, insulin, LH, progesterone, prolactin, parathormone, testosterone, free T3, free T4, TSH and B12 tests were ≥6.

Conclusion: The vast majority of the tests we examined had world-class quality and the quality parameters that needed to be improved were also determined. Sigma methodology, a reliable method, can be used to evaluate, improve and monitor analytical performance, which is part of the total quality of clinical laboratories.