Analysis of a 6-year pilot external quality assurance survey of free light chain using Sigma metrics

Abstract

<jats:title>Abstract</jats:title> <jats:sec id="j_labmed-2018-0175_s_999"> <jats:title id="d2435746e547">Background</jats:title> <jats:p>A pilot external quality assurance (EQA) survey for the free light chain (FLC) assay was developed and implemented in Korea.</jats:p></jats:sec> <jats:sec id="j_labmed-2018-0175_s_998"> <jats:title id="d2435746e555">Methods</jats:title> <jats:p>Survey data over 6 years (2010–2015) were collected retrospectively and Sigma metrics were calculated for method-specific peer groups.</jats:p></jats:sec> <jats:sec id="j_labmed-2018-0175_s_997"> <jats:title id="d2435746e563">Results</jats:title> <jats:p>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.</jats:p></jats:sec> <jats:sec id="j_labmed-2018-0175_s_996"> <jats:title id="d2435746e571">Conclusions</jats:title> <jats:p>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.</jats:p></jats:sec>

Accuracy of determination of free light chains (Kappa and Lambda) in plasma and serum by Swedish laboratories as monitored by external quality assessment

“…The results obtained in our study are similar to those obtained in previous multicentre studies in which the same analytical methods as we have used for measuring serum FLC were compared [23,28]. One study included both samples that were initially submitted for serum FLC analysis or were samples from healthy controls [28], whereas the other study included unselected routine samples submitted for serum FLC analysis [23].…”

“…One study included both samples that were initially submitted for serum FLC analysis or were samples from healthy controls [28], whereas the other study included unselected routine samples submitted for serum FLC analysis [23]. In contrast with the study of Chae et al, our study did not include samples from patients with monoclonal gammopathies and therefore we should not have encountered the problem associated with auto-dilution [28].…”

“…Another possible limitation of the study was the relatively low number of labs participating in this study. Nevertheless, this is more than included in some other multicentre studies [23], although fewer than others [28].…”