Sigma performance evaluations for clinical chemistry and immunoassays in a tertiary care hospital laboratory based on Clinical Laboratory Improvement Amendments (CLIA) 1988 and 2024 Guidelines

Sigma metrics, implemented by clinical laboratories, utilize the performance of assays to evaluate both precision and accuracy by considering the recommended total allowable error (TEa). The study aims to evaluate the performance of 48 analytes (chemistry and immunological) performed in a tertiary care hospital laboratory and compare them with the TEa recommended by CLIA 1988 and 2024 guidelines. This study, conducted at the Biochemistry Department of Medanta Hospital, Lucknow, Uttar Pradesh, India, utilizes retrospective data of the period January 2023 to December 2023 to analyze the performance of 48 assays in terms of precision (percentage of coefficient of variation (CV%) from the internal quality control (IQC) data) and accuracy (Bias %) from the monthly data of external quality assessment services (EQAS). 28 clinical chemistry and 20 immunoassays were performed on an automated VITROS XT 7600 Integrated chemistry analyzer. Sigma scores were calculated and analyzed using a standard formula, which includes Bias%, CV%, and TEa for each assay. Based on TEa source from CLIA 1988 and 2024, for clinical chemistry assays - 64%, 46% showed sigma performance score of >6.0; 27%, 43% showed sigma performance score between 3.0 to 5.9; and 9%, 11% of showed sigma performance score of below 3.0 respectively. For immunoassays, based on TEa source from CLIA 2024, 55% showed a sigma performance score of >6.0, 35% showed a sigma performance score between 3.0 to 5.9, and 10% showed a sigma performance score of below 3.0. This study showed that about 90% of clinical chemistry and immunoassays produced excellent results on the sigma scale. The analysis helped to identify the root causes of the low performance of a few assays with a sigma score below 3.0 and the performance improvement steps undertaken.