Many faces of lupus anticoagulants.

Lupus anticoagulants (LA) are immunoglobulins which inhibit one or more of the in-vitro phospholipid (PL) dependent tests of coagulation. Virtually any physician may encounter LA-positive patients. Such patients present with a variety of diagnostic challenges including arterial and venous thromboembolic events, recurrent fetal loss, TIAs, livedo reticularis, etc. LA and anticardiolipin antibodies (ACA) are the most common cause of acquired thrombophilia. Consequently, it is imperative for clinicians and laboratorians to work together in establishing the diagnosis of LA/ACA. The laboratory diagnosis of LA requires careful adherence to the SSC Subcommittee on Lupus Anticoagulants/Phospholipid-dependent Antibodies guidelines. Four sequential steps are required, including: screening tests, mixing studies (to establish the presence of an inhibitor), confirmatory tests based on increased or altered PL concentrations, and ruling out other coagulopathies (for example, factor VIII inhibitor).