Lupus anticoagulant testing in Belgian laboratories: a comparison with the 2020 International Society on Thrombosis...

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.

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

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%).

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.