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This research aims to evaluate the analytical performance of routine chemistry analytes in a clinical biochemistry laboratory using Six Sigma metrics.

May 9, 2026Open Access

Assessing the analytical performance of the routine chemistry analytes in the clinical biochemistry laboratory by application of Six Sigma metrics

Key Points

This research aims to evaluate the analytical performance of routine chemistry analytes in a clinical biochemistry laboratory using Six Sigma metrics.
Retrospective analysis of internal QC data from July to December 2023
Calculation of Sigma metrics for 16 biochemical analytes using coefficient of variation and total allowable error
Quality goal index analysis performed to identify inaccuracies and imprecisions in analytes with Sigma values <4.
Total bilirubin and triglycerides showed performance of ≥6 sigma.
Sigma values between 3 and 6 were observed for several analytes like glucose and creatinine.
Analytes with Sigma <4 identified issues such as reconstitution errors and temperature fluctuations affecting performance.

Abstract

Abstract Background: Clinical biochemistry laboratory plays a critical role in patient management. Hence, the laboratory must report accurate and reliable results through proper implementation of quality control (QC) practices. This study was conducted to evaluate the analytical performance of routine chemistry analytes in our tertiary care hospital laboratory by the application of Sigma metrics to determine the underlying causes of unsatisfactory performance of analytes with a Sigma value of <4 using quality goal index (QGI) and root cause analysis. Methods: This retrospective study was conducted on data between July and December 2023, available with the department from internal QC data for two levels of controls, and external quality assurance data were collected. Sigma metrics were calculated for 16 biochemical analytes using coefficient of variation, %bias and %total allowable error. QGI analysis was done to analyse imprecision and inaccuracies. Results: Total bilirubin, triglycerides for level 1 (L1) and level 2 (L2) of internal QC (IQC), uric acid (L1) and aspartate aminotransferase (AST) (L2) showed a performance of ≥6 sigma. Sigma was between 3 and 6 for glucose, creatinine, total protein (L1, L2), calcium, AST, alkaline phosphatase (L1) and uric acid (L2), alanine aminotransferase (ALT), ALP, and iron (L2). Sigma was less than 3 for urea, cholesterol, sodium, albumin and potassium (L1, L2), and ALT and iron (L1). For analytes with <4, QGI analysis exposed inaccuracy or imprecision issues and identified errors such as the reconstitution of IQC, storage temperature and fluctuations in instrument performance, which are common causes of poor performance. Conclusions: Six Sigma approach is helpful for quality assurance and identifying areas for improvement. Assessing Six Sigma metrics should be a routine practice to decide the frequency of QC run and to detect errors in analysis.

Assessing the analytical performance of the routine chemistry analytes in the clinical biochemistry laboratory by application of Six Sigma metrics

Key Points

Abstract

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