Sigma metrics in clinical chemistry laboratory – A guide to quality control

Background: Six sigma is a process of quality measurement and improvement program used in industries. Sigma methodology can be applied wherever an outcome of a process is to be measured. A poor outcome is counted as an error or defect. This is quantified as defects per million (DPM). Six sigma provides a more quantitative frame work for evaluating process performance with evidence for process improvement and describes how many sigma fit within the tolerance limits. Sigma metrics can be used effectively in laboratory services. The present study was undertaken to evaluate the quality of the analytical performance of clinical chemistry laboratory by calculating sigma metrics. Methodology: The study was conducted in the clinical biochemistry laboratory of Karwar Institute of Medical Sciences, Karwar. Sigma metrics of 15 parameters with automated chemistry analyzer, transasia XL 640 were analyzed. The analytes assessed were glucose, urea, creatinine, uric acid, total bilirubin (BT), direct bilirubin (BD), total protein, albumin, SGOT, SGPT, ALP, Total cholesterol, triglycerides, HDL and Calcium. Results: We have sigma values <3 for Urea, ALT, BD, BT, Ca, creatinine (L1) and urea, AST, BD (L2). Sigma lies between 3-6 for Glucose, AST, cholesterol, uric acid, total protein(L1) and ALT, cholesterol, BT, calcium, creatinine and glucose (L2).Sigma was more than 6 for Triglyceride, ALP, HDL, albumin (L1) and TG, uric acid, ALP, HDL, albumin, total protein(L2). Conclusion: Sigma metrics helps to assess analytical methodologies and augment laboratory performance. It acts as a guide for planning quality control strategy. It can be a self assessment tool regarding the functioning of clinical laboratory.