Background/Purpose: Local inflammation may cause synovial fibroblasts to become sensitized, resulting in higher susceptibility to arthritis. Longitudinal assessment of joint involvement in rheumatoid arthritis (RA) might show if clinical arthritis tends to recur in the same joints.

Methods: Data from the BeSt study were used, a treat-to-target (disease activity score ≤2.4) study in 508 newly diagnosed RA (ACR 1987 criteria) patients. During 10 years, three-monthly 68-joint assessments (swelling yes/no and Ritchie Articular Index) were done by trained nurses.

We analyzed the association between local joint swelling at baseline and later swelling of the same joint using a multilevel mixed-effects logistic regression model, adjusted for joint location and for timepoint, with joints clustered within patients. A sensitivity analysis was done for the 25% joints that were most often swollen in the study population (MCP 1-3, PIP 2-3, wrists and MTP 2-4).A permutation test was performed to assess if over time joint swelling was better predicted (indicated by a p-value of < 0.05) by baseline swelling of the same joint than by baseline swelling of randomly selected other joints. This was repeated for the joints that were most often swollen.

The association between baseline joint swelling and the number of joint swelling episodes during follow-up was evaluated using a multilevel Poisson regression model, adjusted for joint location and follow-up duration, clustered within patients.

All models were repeated to account for missing data in two ways. First, all missing joint evaluations until end of follow-up were regarded as not swollen. Second, last observation was carried forward for one missing time point if the joint evaluation (swelling yes/no) at the time point before a missing evaluation was the same as at a subsequent time point after the missing evaluation.

Results: At baseline, 8,137/34,423 (24%) assessed joints were scored as swollen. Swelling recurred at least once in 46% of the joints with baseline swelling. Baseline swelling was significantly associated with swelling in the same joint during follow-up (odds ratio 2.37, 95% CI 2.30-2.43, p< 0.001). This association also was found in the 25% most swollen joints (OR 2.11, 95% CI 2.03 to 2.19, p< 0.001). Local joint swelling (in all joints and in the most susceptible joints) was better predicted by baseline swelling of that particular joint than by baseline swelling of other joints (p< 0.001). Baseline joint swelling was also predictive for the number of joint swelling episodes in that joint during follow-up (incidence rate ratio 1.48, 95% CI 1.37 to 1.59, p< 0.001). When accounted for missing data, using the two different methods described before, all models showed similar results.

Conclusion: In RA patients treated to target DAS ≤ 2.4, joint swelling tends to recur locally in the joints swollen at presentation. This suggests that local factors influence the manifestation of joint inflammation over time and might indicate that joints that are swollen at disease onset may require additional monitoring and treatment.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evidence-of-a-tendency-for-localized-recurrence-of-arthritis-in-rheumatoid-arthritis-patients/