Sigma metrics calculation in clinical Biochemistry laboratory - pathway for quality improvement

Abstract

Background: Limitations of Internal quality control (IQC) and external quality assessment system (EQAS) like cost for repeated analysis is a challenge to most of the clinical Biochemistry laboratories. Six sigma system is a part of lean laboratory practices. The higher the sigma value, chance of false test results are less likely. Aim: To calculate sigma metrics of liver function parameters in laboratory and using it to decide on the QC strategy using Westgard Sigma rules for reliable and accurate report. Methods: IQC data for Total bilirubin, Direct bililrubin , AST, ALT, ALP, Total protein & Albumin were analysed for 6 months. Sigma value is calculated and Quality goal index used to identify the reason for low sigma value. Results: Both AST and ALP in level 1 and AST, ALT and ALP in Level 2 has sigma value above 6. Parameters which showed sigma value between 3-6 are ALT and Albumin in Level 1 and BIT and TP in level 2 QC. Parameters which showed sigma value below 3 are BIT, BID & TP in Level 1 &BID and Albumin in Level 2 QC. Conclusion: Appropriate control limits and control measurements can be adapted for each parameters with westgard sigma rule and laboratories can use it as a self-assessment tool.

Keywords

• six sigma
• liver function tests
• quality goal index