Application of sigma metrics in haematology laboratory

Abstract

Objectives: Sigma metrics analysis indicates; the level quality control has achieved and how far a given process deviates from perfection. Though the concept is not new to quality and utility, its implementation in the haematology laboratory is still in its nascent stages. The study aimed to compare the utility of sigma metrics as a comprehensive quality control tool in Haematology laboratory against the current quality tools of Internal Quality Control (IQC) and External quality assurance scheme for haematology analyser.Methods: In the present study, IQC data was analysed from June 2021 to September 2021. Control material included 3 batches of second party controls (SPC). Sigma were calculated for five key haematological parameters run in Sysmex XN 350. OPSpecs charts were prepared. Sigma metrics were calculated using the formula Sigma = (TEa – Bias) / CV, Bias was taken from IQC kit insert. Quality goal index was also calculated when needed.Results: Average sigma metrics achieved for selected parameters was, RBC: 8.1, HB: 7.6, HCT 5.6, PLT: 7.0, and WBC: 6.7. The laboratory has achieved excellent to world class performance in all analytes. Sigma QC rules were applied and modifications proposed to the existing internal QC protocols to reduce the number of rejections.Conclusion: Labs must preferentially use the sigma metrics and sigma QC rules to design its IQC protocols, for individual parameters, rather than follow the ‘one fit for all’ recommendation. This would help save precious time, effort, unnecessary control runs and improve efficiency with better focus on quality control, where required.