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.

• K Cheirmaraj,  
• Bhavana Bais,*  
• Kriti Singh,  
• Varijendra Tripathi

Abstract

Background: 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. Materials and Methods: This study, conducted at Biochemistry Department of Medanta Hospital, Lucknow, Uttar Pradesh, India, utilizes retrospective data of the period January 2023 to December 2023, to analyse performance of 48 assays in terms of precision (percentage of Co-efficient 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 automated VITROS XT 7600 Integrated chemistry analyzer. Sigma scores were calculated and analyzed using standard formula which includes Bias%, CV% and TEa for each assay. Results: 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 sigma performance score of >6.0; 35% showed sigma performance score between 3.0 to 5.9; and 10% showed sigma performance score of below 3.0. Conclusion: This study showed that about 90% of clinical chemistry and immunoassays produced results with excellent performance in sigma scale. The analysis helped to identify the root causes for the low performance of few assays with sigma score below 3.0 and performance improvement steps undertaken.

Keywords

Sigma metrics, TEa, Quality, Accuracy, Precision, Performance, VITROS, CLIA 1988, CLIA 2024