Six sigma in action: Improving cyclosporine drug assay accuracy

Background: Cyclosporine A (CsA) is a narrow therapeutic index immunosuppressant requiring accurate and precise monitoring. This study applied Six Sigma methodology to evaluate and improve the analytical performance of a CsA immunoassay in a tertiary care hospital laboratory. Aims and Objectives: The present study was undertaken to assess the analytical quality of the CsA assay by sigma metric estimation for 5 months. Consequently, a process improvement strategy was implemented over the next 5 months. Materials and Methods: This cross-sectional study was conducted from May 2024 to February 2025 using the Cloned Enzyme Donor Immunoassay on the Indiko Plus analyzer. Sigma metrics were calculated from internal quality control and external quality assurance data for two 5-month phases. The method decision (MEDx) chart was used to visualize performance. A define-measure-analyze-improve-control (DMAIC) strategy was implemented using Westgard rules, Ishikawa diagram, and Pareto analysis to identify and correct performance deficiencies. Results: Pre-intervention mean sigma was 2.87, indicating poor analytical performance. Post-DMAIC intervention, the mean sigma improved significantly to 4.63 (P=0.02), indicating good-to-excellent performance. Bias% was significantly reduced (P=0.03), while the coefficient of variation % remained stable. MEDx charts visually confirmed this performance shift. Conclusion: Six Sigma methodology combined with DMAIC tools significantly enhanced the accuracy and precision of CsA assay performance. This approach provides a robust, scalable framework for quality improvement in clinical laboratories, particularly for assays with critical clinical implications.