Shared epitope and rheumatoid arthritis severity: association with infliximab treatment in a postmarketing study

Background

Modalities of infliximab treatment for active rheumatoid arthritis (RA) have been established following randomised clinical trials.

Objective

In a postmarketing study, we compared the clinical presentation of RA patients from the same geographic area treated by infliximab or not. We checked for markers linked with selection for infliximab treatment focusing on the shared epitope (SE).

Methods

RA patients (897) from the Rhone-Alpes area, France, were enrolled. Clinical indices of disease activity and joint destruction, including age, sex, disease duration, Ritchie articular index, and right Larsen wrist index, were collected. Biological data included erythrocyte sedimentation rate, rheumatoid factor (RF), and SE status. SE determination was performed by enzyme-linked oligosorbent assay.

Results and conclusion

All patients had the typical clinical and biological features of RA. The patients were predominantly white women and 64.6% were RF-positive. The distribution of the SE was 44.74% for 0 copy, 43.33% for 1 copy, and 11.93% for 2 copies. The risk of developing joint destruction was associated with the presence of the SE, with a dose effect. SE heterozygote patients were almost twice as likely to develop erosions as SE-negative patients (OR = 2.18; 95% CI 1.48–3.22, P < 0.001). Patients with two copies of the SE were more likely to develop erosions (OR = 4.73, CI 2.67–8.36, P < 0.001). When patients treated with infliximab were isolated, RA severity parameters, such as the Ritchie and Larsen indices, RF, and the presence of the SE, were associated with infliximab treatment. The frequency of the SE in RA patients treated with infliximab was approximately twice as high for SE heterozygote carriers (OR = 2.18; 95% CI 1.43–3.31, P < 0.001), and 4 times as high for SE homozygotes (OR = 3.88; 95% CI 2.25–6.68, P < 0.001). Thus RA patients with the SE were more often selected for infliximab treatment extending the link between SE and severity.