ABSTRACT
The study of the epidemiology of the antiphospholipid syndrome (APS) and of antiphospholipid antibodies (aPL) is in its infancy. Classification criteria for the APS have followed a traditional approach of selecting clinical features determined clinically to be characteristic of APS, but APS classification criteria differ from established classification criteria for other rheumatic diseases in several ways. Patients with a positive antinuclear antibody test, false-positive test for syphilis, thrombocytopenia, and hemolytic anemia could easily fall under the rubric of "primary" or "secondary" APS. Retrospective or cross-sectional studies allow only an estimate of the prevalence of APS in patients who have aPL. The natural history and prognosis of patients with APS who present with stroke also have been extensively studied. Two recent studies, one of APS patients with both arterial and venous events, and one of APS patients with venous events, have addressed the natural history of recurrent thrombotic events in patients already diagnosed with APS.
