Performance Evaluation of HemosIL Free Protein S

Abstract

Purpose: It is necessary to measure free protein S antigen levels in plasma for diagnosing protein S deficiency. The aim of this study was to evaluate the performance of HemosIL Free Protein S reagent (Instrumentation Laboratory, Lexington, MA, USA) which is an automated latex ligand immunoassay for the quantitative determination of free protein S. Methods: HemosIL Free Protein S was evaluated for its precision, linearity, and reference range and compared to the HemosIL ProS, which is a reagent for the measurement of protein S activity in plasma, following the Clinical and Laboratory Standards Institute guidelines. The HemosIL Free Protein S was also compared to the STA-Liatest Free Protein S (Diagnostica Stago, Taverny, France), which is another reagent used in testing free protein S antigen levels. Results: The within-run, between-run, and total coefficients of variation (CV) for HemosIL Free Protein S assay were 5.3%, 5.9%, and 7.9% at the low level, respectively, and 3.3%, 2.4%, and 4.1% at the high level, respectively. The linearity was in the range of 10.9-126.1% with a high correlation coefficient (R) of 0.997. The comparison between HemosIL Free protein S and ProS showed good correlation (R = 0.866). An excellent correlation (R = 0.931) was found between HemosIL Free protein S and STA-Liatest Free Protein S. The reference ranges for women and men were 50.8-116.9% and 69.4-138.3%, respectively. Conclusion: HemosIL Free Protein S for measuring free protein S antigen in plasma had excellent precision and linearity. HemosIL Free Protein S was considered useful in detecting protein S deficiency.