The term “antiphospholipid syndrome” originally described the clinical association between antiphospholipid antibodies and a syndrome of hypercoagulability. The criteria for diagnosis of antiphospholipid syndrome and the terminology of the disease have evolved over the years as the relevant pathophysiology and immunology have become better understood. Levine and colleagues discuss antiphospholipid syndrome, an uncommon (but not rare) disease with serious risks of arterial and venous thrombosis as well as recurrent pregnancy loss.

The most recent international consensus criteria for diagnosing antiphospholipid syndrome require the presence of a clinical and a laboratory marker of the syndrome before a definitive diagnosis can be made. The most sensitive laboratory test for antiphospholipid syndrome is the presence of anticardiolipin antibodies; however, lupus anticoagulant is a more specific sign. In large studies, as many as 5 percent of healthy control subjects have at least one of the autoantibodies associated with antiphospholipid syndrome. Most of these persons never develop any thrombotic or obstetric complications. Anti-β₂-glycoprotein I autoantibodies are another class of autoantibodies strongly associated with the syndrome, but they are not presently included in the consensus criteria.

Antibody screening is typically performed in persons with early or recurrent thrombotic episodes. The authors note that the risk of clinical sequelae is most elevated in persons with laboratory evidence of antiphospholipid syndrome and additional risk factors that predispose to thrombosis (e.g., oral contraceptive use, immobility) or atherosclerotic damage to blood vessels (e.g., hyperlipidemia, smoking, diabetes).

Both arterial and venous thromboses can be present in patients with antiphospholipid syndrome and can involve virtually any organ. Deep venous thrombosis of the leg is the most common venous occlusion, while stroke and transient ischemic attacks are the most frequently occurring arterial complications. Other signs in patients with antiphospholipid syndrome are concomitant thrombocytopenia and hemolytic anemia.

Treatment of the syndrome centers on anticoagulant therapy. Aspirin may be helpful in preventing fetal loss, but it does not appear to protect against other thrombotic disease. Low-intensity warfarin therapy (to attain an International Normalized Ratio [INR] of less than 1.9) is also not protective. It remains unclear whether moderate-intensity warfarin therapy (INR of 2.0 to 2.9) is preferable to high-intensity anticoagulation (INR of 3.0 or more). The review adds that modification of other thrombotic or atherosclerotic risk factors (e.g., avoiding oral contraceptive use, treatment of hyperlipidemia, smoking cessation) is also important in decreasing the overall risk of clinical complications.