Tumour necrosis factor inhibitor exposure and radiographic outcomes in Veterans with rheumatoid arthritis: A longitudinal cohort study

Objectives. The aim was to estimate the impact of TNF inhibitor (TNFi) exposure on radiographic disease progression in US Veterans with RA during the first year after initiating therapy. Methods. This historical longitudinal cohort design used clinical and claims data to evaluate radiographic progression after initiation of TNFi. US Veterans with RA initiating TNFi treatment (index date), 6months pre-index and 12months post-index VA enrolment/activity, and initial (6months pre-index to 30 days post-index) and follow-up (10 18months post-index) bilateral hand radiographs were eligible. The cumulative TNFi exposure and change in modified Sharp score (MSS) between initial and follow-up radiographs were calculated. The percentage of patients with clinically meaningful change in MSS (5) for each month of exposure was assessed using a longitudinal marginal structural model with inverse probability of treatment weights. Mean values and CIs were generated using 1000 bootstrapped samples. Results. For 246 eligible patients, the mean (S.D.) age was 58 (11) years; 81% were male. The mean (S.D.) initial MSS was 19.6 (33.4) (range 0 214). The mean change (S.D.) in MSS was 0.3 (3.6) (median 0, range 19 to 22). Patients with the greatest exposure had the least radiographic progression for both crude and adjusted model analyses. Adjusted rates of MSS change 5 points (95% CI) were 10.6% (9.8%, 11.4%) for patients with 3months of exposure compared with 5.4% (5.1%, 5.7%) for patients with 12months of exposure. Conclusion. One-year changes in radiographic progression were small. Patients with the greatest cumulative TNFi exposure experienced the least progression.