Analysis of Laboratory Quality Control Performance: A Six-Month Six-Sigma Metric Study

The Sigma Metric is a crucial tool for evaluating laboratory quality control (QC) performance, providing a standardised measure of analytical process capability. This manuscript presents a comparative analysis of sigma values for routine chemistry parameters (29 analytes) between January and July at our laboratory using two levels of controls. The objective was to assess changes in analytical performance over a six-month period. Data were analysed from January and June, followed by July, with sigma values calculated based on internal QC and proficiency testing data. The findings clearly highlight the laboratory’s strong analytical capability, with the majority of analytes (25 analytes) achieving Six-Sigma performance — reflecting excellent precision, accuracy, and process stability. A few parameters (4 analytes) showed sigma values in the 3–5 range, which served as constructive indicators for fine-tuning existing processes. We took additional measures for these selected parameters by consistently following maintenance guidelines and improving QC storage and water quality, which led to an upward trend in sigma values for these analytes in July. These findings underscore the dynamic nature of laboratory performance and the importance of maintaining high-quality patient care.