Pulmonary function trajectories in rheumatoid arthritis-associated interstitial lung disease

Interstitial lung disease (ILD) is a serious complication of rheumatoid arthritis (RA). The aim of this study was to compare pulmonary function trajectories in RA-ILD, focusing on the impact of oral corticosteroid therapy and radiographic pattern.

We used a multiple regression model with line artime trend and individual random coefficients for intercept and slope to assess forced vital capacity (FVC) and diffusing capacity of the lungs for carbon monoxide (DLCO), allowing the description of individual linear patterns and systematic differences at a group level.

We included 101 patients with RA-ILD retrospectively. Mean FVC and DLCO were lower in patients who received corticosteroid therapy for ILD than in untreated patients (79% vs 95% predicted, and 48% vs 58% predicted). The change in FVC per 30 days was -0.10 [95% confidence interval (95% CI) -0.18; -0.04] in the treated and -0.13 (95% 20 CI -0.19; -0.07) in the untreated group. The between-group difference was not significant (-0.03, 95% CI -0.12; 0.06, p = 0.571). For DLCO, the change per 30 days was -0.10 (95% CI -0.15; -0.04) in the treated and -0.10 (95% CI -0.14; -0.05) in the untreated group, with no significant between-group difference (0.0007, 95% CI -0.07; 0.07, p = 0.985). Inclusion of radiographic pattern did not change the results.

The rate of pulmonary function decline was similar for corticosteroid-treated and untreated patients, although treated patients had significantly lower pulmonary function. This may indicate a limited disease-modifying effect in RA-ILD, but further studies are needed.