Lupus anticoagulants: diagnostic dilemma and clinical challenge.

Lupus anticoagulants (LAs) are immunoglobulins which prolong 1 or more of the in vitro phospholipid-dependent tests of coagulation (e.g., activated partial thromboplastin time [APTT], dilute Russell viper venom time [dRVVT], kaolin clotting time [KCT], and textarin time [TT]). Paradoxically, patients with LAs rarely experience hemorrhagic problems. Approximately 1/3 of individuals with LAs experience thromboembolic complications such as stroke, deep vein thrombosis, and pulmonary emboli. LAs are members of the antiphospholipid antibody (APA) family. The APA family includes: LAs, anticardiolipin antibodies (ACAs), and reagin (the antibody responsible for the positive serologic test for syphilis). In approximately 60% of the patients, a LA and an ACA will both be present. The diagnosis of LAs requires an organized approach. Careful preparation of platelet poor plasma (PPP) is essential to assure maximum detection of LA. In order to rule out LAs, it is necessary to perform at least 2 screening tests (e.g., APTT, dRVVT). Additional steps in the diagnosis of LAs include mixing studies to identify the presence of an inhibitor and confirmatory procedures to demonstrate phospholipid-dependence of the inhibitor. It is also important to rule out any other potential coagulopathies which may account for the prolonged screening studies.