Objective: To determine whether joint destruction, indication for, and response to infliximab in rheumatoid arthritis are associated with the shared epitope (SE) or selected cytokine gene polymorphisms (interleukin (IL) 1B, IL1-RN, and tumour necrosis alpha).
Methods: In a large rheumatoid arthritis population of 930 patients from the same area (Rhône-Alpes, France), patients with (n = 198) or without infliximab treatment (n = 732) were compared according to their genetic status. Clinical, biological, and radiological data were collected. Typing for SE status and cytokine polymorphisms was carried out using enzyme linked oligosorbent assay. Statistical analysis was by chi(2) testing and calculation of odds ratios (OR).
Results: A dose relation was observed between the number of SE copies and joint damage in the whole rheumatoid population (OR, 1 v 0 SE copy = 2.38 (95% confidence interval, 1.77 to 3.19), p<0.001; OR 2 v 0 SE copy = 3.92 (2.65 to 5.80), p<0.001. The SE effect increased with disease duration but was not significant before two years. Selection for infliximab treatment (n = 198) was associated with increased disease activity, joint damage, and the presence of the SE with a dose effect. In all, 66.2% patients achieved an ACR20 improvement. No clinical or genetic factors were able to predict the clinical response to infliximab.
Conclusions: This post-marketing study in a large cohort of rheumatoid arthritis patients indicates a linkage between rheumatoid arthritis severity, selection for treatment with infliximab, and the presence and dose of the SE.