Lupus anticoagulant: performance of the tests as recommended by the latest ISTH guidelines

Objectives: Lupus anticoagulant (LA) is clinically the most relevant among all antiphospholipid antibody tests. Recently, new guidelines for LA detection were published. The objective of this retrospective cohort study was to compare tests recommended under these guidelines with other methods used for LA detection. Methods: The study group consisted of 336 subjects suffering from various autoimmune diseases. We used activated partial thromboplastin time (aPTT), diluted Russell viper venom time (dRVVT) and diluted prothrombin time (dPT) tests for LA detection together with a ratio between sensitive and insensitive aPTT reagent. We also tested if LA was dependent on beta(2)glycoprotein I (beta(2)GPI) using one of the recently described methods. Results: All LA tests performed were associated with a history of thrombosis. The highest odds ratio (OR) for thrombosis was found for beta(2)GPI-dependent LA but sensitivity was low (OR = 8.4; specificity/sensitivity = 98%/15%). All LA tests showed a much stronger association with thrombosis than with pregnancy failure. Conclusions: LA tested by aPTT and/or dRVVT (at least one out of two tests positive), as recommended by the guidelines, was associated less strongly with a history of thrombosis (OR = 4.1) than either of these tests separately (OR = 5.0 and 4.3, respectively). With both tests positive ('double LA positivity') the association with thrombosis was stronger (OR = 6.5) compared with only one positive test. In fact, 'double LA positivity', detected by combinations of any of the tests studied, was markedly associated with a history of thrombosis.