Diagnosis of antiphospholipid syndrome.

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by recurrent vascular thrombosis and pregnancy losses. Laboratory diagnosis of APS relies on the demonstration of a positive anticardiolipin antibody test by an in-house or commercially available enzyme-linked immunosorbent assay, or on the presence of lupus anticoagulant by a coagulation-based test. Persistence of the positive results must be demonstrated, and other causes and underlying factors considered. Although it is universally recognized that the routine screening tests (anticardiolipin antibody or lupus anticoagulant) might miss some cases of APS, careful differential diagnosis and repeat testing are mandatory before the diagnosis of 'seronegative APS' can be made. Correct identification of patients with APS is important because prophylactic anticoagulant therapy can prevent thrombosis from recurring and treatment of affected women during pregnancy can improve fetal and maternal outcome.