Performance Assessment of Staclot-LA Assay on Fully Automated Coagulation Analyser for Lupus Anticoagulant Testing Using Internal and External Quality Controls.

INTRODUCTION It is recommended to detect lupus anticoagulant (LA) using two phospholipid-dependent clotting assays, including a LA-sensitive activated partial-thromboplastin-time (aPTT). Among these reagents, Staclot-LA assay is performed on a mixture of test and normal plasma with and without hexagonal phase phospholipids. However, its lack of validation on automated coagulation analyser is a major drawback. We aimed i/to assess the analytical performance of Staclot-LA assay on automated system; ii/to compare inter-laboratory agreement of Staclot-LA performed on semi-automated or fully automated analysers using two external-quality-assurance (EQA) programs data.

Methods

We adapted the Staclot-LA assay (Stago) set-up on a STA-R-Max analyser and locally validated the manufacturer's recommended cut-off for positive LA testing using samples from healthy volunteers. Reproducibility and accuracy were assessed using internal quality controls (IQC, Staclot-LA1/LA2) over a five-year period. Staclot-LA results from EQA Probioqual and ECAT were compared between semi- and fully-automated analysers.

Results

Agreement of our LA results (positive or negative) was observed in 100% of IQC (n = 130) and EQA (n = 58) samples. Probioqual and ECAT interlaboratory Staclot-LA results showed full agreement for 96.2% and 89.7% in semi-automated system users vs 96.7% and 92.5% in automated system users. The system had no significant impact on the qualitative results (Probioqual p = 1.000; ECAT p = 0.5912), even though we observed increasing biases of the differences in clotting times, especially in LA positive samples on automated vs semi-automated analysers.

Conclusion

Staclot-LA assay can be reliably performed on a fully automated system, thus paving the way for wider accessibility and widespread use.