Predictors of Progression and Mortality in Patients with Prevalent Rheumatoid Arthritis and Interstitial Lung Disease: A Prospective Cohort Study

Objectives: To describe a prospective cohort of patients with rheumatoid arthritis associated with interstitial lung disease (RA-ILD) and identify risk factors associated with disease progression and mortality in this cohort. Patients and methods: We performed a multicenter, prospective, observational study of patients with RA-ILD receiving disease-modifying antirheumatic drugs (DMARDs) between 2015 and 2020. The patients were assessed using high-resolution computed tomography and pulmonary function tests at baseline and at 60 months. The main endpoint was “Progression to ILD at the end of follow-up” in terms of the following outcomes: (1) improvement (i.e., improvement in forced vital capacity (FVC) ≥10% or diffusing capacity of the lungs for carbon monoxide (DLCO) ≥15% and absence of radiological progression); (2) nonprogression (stabilization or improvement in FVC ≤10% or diffusing capacity of the lungs for carbon monoxide (DLCO) <15% and absence of radiological progression); (3) progression (worsening of FVC >10% or DLCO >15% and radiological progression); or (4) death. We recorded demographic and clinical characteristics, lung function, and the incidence of adverse events. A Cox regression analysis was performed to identify factors associated with the worsening of ILD. Results: After 60 months, lung disease had stabilized in 66 patients (56.9%), improved in 9 (7.8%), and worsened in 23 (19.8%). Eighteen patients (15.5%) died, with a mean survival of 71.8 (1.9) months after diagnosis of ILD. The Cox multivariate analysis revealed the independent predictors of worsening of RA-ILD to be usual interstitial pneumonia (hazard ratio (HR), 2.6 (95%CI, 1.0–6.7)), FVC <80% (HR, 3.8 (95%CI, 1.5–6.7)), anticitrullinated protein antibody titers (HR, 2.8 (95%CI, 1.1–6.8)), smoking (HR, 2.5 (95%CI, 1.1–6.2)), and treatment with abatacept, tocilizumab, or rituximab (HR, 0.4 (95%CI, 0.2–0.8)). During follow-up, 79 patients (68%) experienced an adverse event, mostly infection (61%). Infection was fatal in 10/18 patients (55.5%) during follow-up. Conclusions: Lung function is stable in most patients with RA-ILD receiving treatment with disease-modifying anti-rheumatic drugs (DMARDs), although one-third worsened or died. Identifying factors associated with worsening in RA-ILD is important for clinical management.