The epidemiology of the antiphospholipid syndrome: who is at risk?

Arterial and venous thrombosis are the most common and clinically relevant events of the so-called antiphospholipid syndrome; they are reported in approximately one third of patients with the antiphospholipid (aPL) antibodies. APL antibodies are part of a wide family of immunoglobulins directed against proteins complexed with negatively charged phospholipids. They include lupus anticoagulants (LA), anticardiolipin (aCL) antibodies, and the most recently recognized anti-beta-2-glycoprotein I (beta 2-GPI) and antiprothrombin (aPT) antibodies. Previous thrombotic events and the presence of LA, particularly if identified by the dilute Russell viper venom test, appear to be the strongest risk factors for vascular complications. High-titer aCL antibodies have been reported to be associated with an increased thrombotic tendency, but this was not confirmed in all studies. The data only partially support the concept that anti-beta 2-GPI and aPT antibodies may be considered as independent risk factors for thrombosis. Further prospective studies are required.