Evaluation of Performance of Internal Quality Control in A Clinical Chemistry Laboratory Using Six Sigma-A Retrospective Analysis

Objective : Medical laboratories play a vital role in clinical decision making. Stringent quality assurance in testing laboratory is required in all phases. With the advent of automation a reduction of variation has been seen. Six sigma is one metric of laboratory performance which aims to fit at least six standard deviations of an assay within defined total allowable error characteristics of each assay. In this study we evaluated six sigma metrics for 21 clinical biochemistry parameters in order to analyze our performance. Methodology: We conducted a retrospective data analysis from March November 2020 in Tata Medical Center, Kolkata. Total allowable error (TEa) considered as per (CLIA)-88 Proficiency Testing Criteria. Coefficient of variance (CV) calculated from monthly internal quality control data. Bias percentage for each parameter calculated from a commercially available proficiency testing scheme. Sigma metrics and Quality goal index (QGI) calculated using TEa%, Bias% and CV%. Result: For lower level internal quality control, ten out of the 21 analytes achieved high six sigma quality performance. Nine analytes showed very good performance and two analytes failed minimum sigma quality performance. For higher level control the data collected indicated that sixteen out of 21 analytes qualified six sigma quality performances, four analytes had very good performance and one analyte had less than desirable sigma metrics. Conclusion: In our study lipase found to be the best performer and bicarbonate found to be poor performer on sigma metric analysis. Therefore sigma metric analysis can help evaluate the performance of laboratory.