Objective: To test the Sapporo criteria for the classification of the antiphospholipid syndrome (APS).
Methods: We classified 243 consecutive patients who had clinical diagnoses of primary APS (n = 49), secondary APS (n = 26), systemic lupus erythematosus (SLE) without clinical APS (n = 131), and lupus-like disease without clinical APS (n = 37).
Results: Sensitivity, specificity, positive predictive value, and negative predictive value were 0.71, 0.98, 0.95, and 0.88, respectively. False-negative findings were the result of patients being classified on the basis of minor criteria that were not included in the Sapporo criteria, such as livedo reticularis, thrombocytopenia, low-titer IgG or IgM anticardiolipin antibody, IgA anticardiolipin antibody, and anti-beta2-glycoprotein I antibody. Some patients with false-negative results were true seronegative cases.
Conclusion: The Sapporo criteria for APS compare favorably with the American College of Rheumatology criteria for SLE and are usable for clinical studies.