Comparison of the 1999 Sapporo and 2006 revised criteria for the classification of the antiphospholipid syndrome.

OBJECTIVES The 2006 revised criteria for antiphospholipid syndrome (APS) provide a new classification challenge, and studies validating the updated criteria against the older ones are still scanty. We compared the 1999 preliminary with the 2006 revised classification criteria for APS, and evaluated if the revised criteria provide an added value over the original ones. METHODS A laboratory-based registry population was obtained on the basis of the positivity of antiphospholipid (aPL) antibodies. Patients were analysed for fulfillment of the 1999 and 2006 classification criteria for APS, non-criteria features of APS, and autoantibody profile. RESULTS Of 144 aPL-positive identified patients, 119 had at least 2 aPL tests on separated occasions, and were included in this study. According to the 1999 criteria, 23 patients had APS (15 had thrombosis alone, 4 pregnancy morbidity, and 4 both); while 26 fulfilled the 2006 revised criteria (15 had thrombosis alone, 5 pregnancy morbidity, and 6 both). One patient with isolated thrombosis who met 1999 criteria did not meet those of 2006 (aCL positivity but not >12 weeks apart). One patient with thrombosis, other with pregnancy morbidity, and 2 with both only fulfilled the 2006 criteria because they had isolated anti-Beta(2)GPI antibody-positivity. High concordance between criteria was found, with kappa index of 0.87 (95%; CI, 0.76-0.98). CONCLUSIONS The 2006 revised criteria represent a step-forward since it allows the inclusion of patients with anti-Beta(2)GPI antibodies as an isolated serological feature. However, a wider time interval between serologic tests seems unlikely to make differences.