Interstitial Lung Disease in Patients With Rheumatoid Arthritis or Psoriatic Arthritis Initiating Biologics and Controls: Data From 5 Nordic Registries

OBJECTIVE: Interstitial lung disease (ILD) is one of the most common pulmonary manifestations of rheumatoid arthritis (RA), but its prevalence has not been investigated in psoriatic arthritis (PsA). The role of methotrexate (MTX) in ILD development remains under debate. This study (1) compares the incidences of ILD in patients with RA or PsA initiating a first biologic disease-modifying antirheumatic drug (bDMARD) to that in the general population, and (2) investigates the role of MTX comedication on ILD incidence. METHODS: Patients were identified in 5 rheumatology registries. Demographics, MTX use, and disease activity were retrieved. Matched subjects from the general population were available from 4 countries. Incidence of ILD during follow-up of up to 5 years was assessed through national patient registries. Subjects with prior ILD were excluded. Adjusted hazard ratios (HRs) were calculated for ILD incidence in patients vs the general population, and for MTX users vs nonusers. RESULTS: During follow-up of 29,478 patients with RA and 10,919 patients with PsA initiating a first bDMARD and 362,087 population subjects, 225, 23, and 251 cases of ILD were identified, respectively. HRs for ILD (vs population subjects) were 9.7 (95% CI 7.97-11.91) in RA and 4.4 (95% CI 2.83-6.97) in PsA. HRs for ILD with MTX comedication (vs nonuse) were 1.0 (95% CI 0.72-1.25) in RA and 0.9 (95% CI 0.38-2.05) in PsA. CONCLUSION: Among patients with RA and PsA initiating a bDMARD, the risk of ILD was higher than in the general population, and was highest in RA. MTX comedication was not a risk determinant for ILD.