Objective: To determine the frequency and clinical impact of anticardiolipin antibodies (aCL) in patients with rheumatoid arthritis treated with infliximab and etanercept.
Methods: 121 patients from the Stockholm tumour necrosis factor alpha (TNFalpha) follow up registry (STURE) treated with infliximab or etanercept were studied.
Results: At baseline 9/65 (14%) infliximab and 10/56 (18%) etanercept treated patients had positive aCL. After 3 months the frequencies of aCL positivity were 29% (p<0.05 compared with baseline) and 27%, respectively, and after 6 months 28% and 25%. Increases were seen for both IgG and IgM aCL. Increasing age, a higher number of prior DMARDs, and higher DAS28 were predictors for the development of aCL. In the infliximab treated patients, 26/30 (87%) aCL(-) but only 7/14 (50%) aCL(+) patients met the ACR20 criteria (p<0.05), and the frequency of treatment limiting infusion reactions in the aCL(+) patients was higher than expected (17%). aCL positivity in the etanercept treated patients did not show such a clinical correlate. Four patients had thromboembolic events, of whom two were aCL(+) and two aCL(-).
Conclusion: Frequencies of both IgM and IgG aCL positivity increase in patients treated with these TNFalpha antagonists for 3 months or longer. Increasing age, a greater number of prior DMARDs and a greater disease activity at baseline are predictors for the development of aCL. The development of aCL during treatment with infliximab, but not etanercept, is associated with worse clinical results and more frequent serious infusion reactions. aCL are an important class of autoantibodies associated with TNFalpha blocking therapy.