Lupus anticoagulant testing in Belgian laboratories: a comparison with the 2020 International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (ISTH-SSC) guidelines

Abstract

Objectives: We investigated lupus anticoagulant (LA) testing in Belgium and verified these findings against the 2020 International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (ISTH-SSC) Guidelines.

Methods: A survey, interrogating pre- and post-analytical aspects of antiphospholipid antibodies, including LA analysis, was distributed to all Belgian laboratories (n = 111).

Results: About 66% of the laboratories responding to the entire survey (58%) performed LA analysis. About 78% used thrombocyte-free citrated plasma. Most (90%) used the combination of dilute Russell's viper venom time (dRVVT) and activated partial thromboplastin time (aPTT), performing dRVVT (82%) and aPTT (78%) if the screening test was prolonged. A variety of instrument/reagent combinations were used. Normal pooled plasma (PNP) for mixing tests was used by 83%, either commercially lyophilized (56%) or frozen (44%), mostly (98%) in a 1:1 PNP: patient plasma ratio. Interpretation was based on normalized clotting time ratio, using manufacturers' or own study data as cutoff values. About 61% gave a final conclusion. About 88% added comments, mainly (94%) with a positive result. All laboratories programmed a barring period after an initial positive result. About 66% performed LA detection in patients receiving direct oral anticoagulants, 74% after using sample pretreatment with active charcoal absorption. LA testing for vitamin K antagonists and heparin-treated patients was done by 54%, regardless of international normalized ratio (64%) or anti-FXa results (82%).

Conclusions: The survey shows adherence to ISTH-SSC guidelines, especially for sample preparation and test methodologies. Additional efforts are required to harmonize LA detection in anticoagulated patients and result interpretation.

Keywords: Antiphospholipid syndrome; clinical laboratory techniques; cutoff value; lupus anticoagulant.