Antiphospholipid antibodies and antiphospholipid syndrome in patients presenting with immune thrombocytopenic purpura: a prospective cohort study

The pathogenetic role and the clinical importance of the presence of antiph ospholipid antibodies (APAs) in patients with immune thrombocytopenic purpu ra (ITP) are not clear. In this study, the prevalence and clinical signific ance of APAs were investigated in patients with ITP. Eighty-two newly diagn osed ITP patients were prospectively studied. They were evaluated for the p resence of lupus anticoagulant (LA) and immunoglobulin G/M anticardiolipin antibodies (ACAs). Thirty-one patients (37.8%) were APA positive at diagnos is. No statistically significant differences were found between the APA-pos itive and APA-negative groups regarding gender, initial platelet counts, or response to methylprednisolone therapy. After 5 years of followup, cumulat ive thrombosis-free survival of APA-positive (n = 31) and APA-negative (n = 51) ITP patients was 39% and 97.7%, respectively. A significant difference was found between these groups by log-rank test (P = .0004). In addition, LA was an important risk marker for the development of thrombosis in ITP pa tients. After a median follow-up of 38 months, 14 ITP patients (45%) who ha d APA positivity developed clinical features (thrombosis or fetal losses) o f anti phospho lipid syndrome (APS). There were no differences between the APA-positive patients with and without APS regarding the initial Platelet c ounts, response to the therapy, or ACA positivity. The positivity rate for LA was significantly higher in those patients with ITP who developed APS (c hi (2): P = .0036; relative risk 7.15; 95% confidence interval, 1.7-47). In conclusion, this study indicates that a significant proportion of patients initially presenting with ITP and APA positivity developed APS. In patient s with ITP, the persistent presence of APAs is an important risk factor for the development of APS. (C) 2001 by The American Society of Hematology.