Assessment of analytical process performance using the Six Sigma method: A comparison of two biochemistry analyzers

INTRODUCTION: Six Sigma is a method of quality management analysis that integrates accuracy and precision of measurement, error identification, and process improvement. The aim of this study was to evaluate the analytical process performance of routine biochemical tests performed with 2 biochemistry analyzers in our laboratory according to Six Sigma methodology and compare the findings.
METHODS: Internal quality control (IQC) data of routine biochemical analytes used for 3 months in 2 Abbott Architect c16000 analyzers (Abbott Diagnostics Inc., Lake Forest, IL, USA) were extracted and the mean, SD, coefficient of variation %, bias % and sigma values were calculated. The performance of the analytes was classified according to the sigma level: <3 demonstrated poor performance, 3-6 was graded as acceptable, and >6 indicated good performance.
RESULTS: For both analyzers, 2 levels IQC sigma values of chloride and sodium were <3, while the levels of alkaline phosphatase, aspartate aminotransferase, amylase, creatine kinase, iron, gamma-glutamyl transferase, and magnesium were >6; and the sigma values of total bilirubin, phosphorus, glucose, high-density lipoprotein-cholesterol, total cholesterol, calcium, creatinine, and total protein were determined to be within the acceptable range of 3-6. Amylase and creatine kinase were the best performers on both analyzers, while sodium had the lowest sigma values.
DISCUSSION AND CONCLUSION: Six Sigma is a good method to evaluate the analytical process performance of a clinical laboratory. Quality control measures should be implemented for parameters with low sigma values.