Update on laboratory practice for the diagnosis of lupus anticoagulant and the antiphospholipid syndrome

Antiphospholipid syndrome (APS) is defined as an autoimmune and prothrombotic disorder in patients with the persistent presence of antiphospholipid antibodies (aPLs). In the classification criteria, aPL expresses lupus anticoagulant (LA) activity, which is detected by prolongation of coagulation assays. The LA detection algorithm is a sequential flow including screening tests, mixing tests, and confirmatory tests to differentiate between LA-positive and other anticoagulant abnormalities. Two types of assays are used, like dilute Russell’s viper venom time (dRVVT) and activated partial thromboplastin time (APTT) because no single test is sensitive to all LAs. The anticoagulant drugs prescribed for the prevention and treatment of thrombosis disorders can interfere with the assays, and it is important to know the effects of these drugs in the assays. Especially, new generation anticoagulant drugs, called direct oral anticoagulants (DOACs), affect the results. In this review, the following points are discussed: i) LA detection flow and data interpretation, ii) the principles of coagulation assays proposed and their characteristics, and iii) the effects of anticoagulant drugs in LA detection.