Risk factors for interstitial lung disease in rheumatoid arthritis: a cohort study from the KOBIO registry.

Background: Interstitial lung disease (ILD) is a critical extra-articular manifestation of rheumatoid arthritis (RA). However, little is known about the risk factors of RA-ILD.

Objectives: Here, we examined the effect of demographic, clinical, therapeutic, and environmental factors on the incidence of ILD in RA patients using the Korean College of Rheumatology Biologics and Targeted Therapy (KOBIO) registry.

Design: We used data from the KOBIO registry, a multi-center, prospective, observational cohort that included RA patients in South Korea.

Methods: RA patients who used biologic or targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) or conventional synthetic (cs)DMARDs, and were enrolled in the KOBIO registry, were examined. Demographic, clinical, and radiographic characteristics, as well as medications, were recorded at baseline and annually thereafter. Kaplan-Meier curves and the log-rank test were used to compare the incidence of ILD between RA patients taking different b/tsDMARDs. Hazard ratios (HRs) were calculated by Cox regression analyses.

Results: In total, 2492 patients (1967 in the b/tsDMARDs group and 525 in the csDMARDs group) were analyzed. The b/tsDMARDs group showed longer disease duration, higher erythrocyte sedimentation rate/C-reactive protein, and higher disease activity score-28 (DAS28) than the csDMARDs group. The incidence of ILD was significantly higher in those taking tumor necrosis factor inhibitors and abatacept than in those taking csDMARDs (log ranked  < 0.001). Multivariate Cox regression analysis identified older age (HR = 1.057,  = 0.001), male sex (HR = 2.824,  = 0.007), time-averaged DAS28 (HR = 2.241,  < 0.001), and rheumatoid factor titer (HR = 1.009,  = 0.007) as having a significantly increased HR for ILD occurrence.

Conclusion: ILD is a rare but critical extra-articular symptom of RA patients. Therefore, RA patients with the above risk factors should be monitored carefully for ILD development.