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The application of Sigma metrics can be used for assessing the performance of diagnostic laboratories. Clinical laboratories are confronted with the trouble of having to select the best and suitable quality specifications that are required for quality planning. In this regard, our study aims at evaluating the performance of Sysmex XN-1000 hematology analyzer by using Sigma metrics based on different total allowable error (TEa) source and to determine the effects of these variations in Sigma metric evaluation.

Background: A pilot external quality assurance (EQA) survey for the free light chain (FLC) assay was developed and implemented in Korea. Methods: Survey data over 6 years (2010–2015) were collected retrospectively and Sigma metrics were calculated for method-specific peer groups. Results: Nineteen to 29 laboratories participated in the EQA survey, and nephelometric (20%) and turbidimetric (80%) methods were used. Using a previously published clinically relevant reference change value (RCV) of 54.5% as the tolerance limit, the method-specific median Sigma metrics of kappa (κ) and lambda (λ) FLC achieved greater than Three-Sigma for 86–97% of all EQA distributions, and Five-Sigma for 48–72% of all distributions. Conclusions: This EQA analysis of FLC assay applied clinically relevant quality specifications using Sigma metrics. During the 6-year EQA survey, we found that most of the results from participating laboratories meet clinically relevant quality specifications. In addition, method-specific differences were noted for λ FLC, at FLC concentrations above the initial measuring range that require a sample dilution. [ABSTRACT FROM AUTHOR]