Risk of serious infection in patients with rheumatoid arthritis-associated interstitial lung disease or bronchiectasis: A comparative cohort study.

To investigate the association between rheumatoid arthritis-associated lung disease (RA-LD) and serious infection risk. We conducted a retrospective cohort study using the MGB Biobank (Boston, Massachusetts), comparing RA-LD to RA patients without lung disease (RA-no LD), matched by age, sex, and RA duration. RA-LD cases were verified by medical record review and chest imaging for clinically apparent RA-associated interstitial lung disease (RA-ILD) and/or RA-associated bronchiectasis (RA-BR). The primary outcome was serious infection. Incidence rates and propensity score-adjusted subdistribution hazard ratios (sdHR) were calculated using Fine and Gray models to account for competing risk of death. Among 221 RA-LD cases (151 RA-ILD and 70 RA-BR) and 980 RA-no LD comparators, RA-LD had a significantly higher serious infection risk compared to RA-no LD comparators (55.8 vs. 25.8 per 1,000 person-years, sdHR 1.60, 95%CI 1.20-2.12). The increased risk remained significant for RA-ILD cases (sdHR 1.79, 95%CI 1.33-2.41), but not for RA-BR (sdHR 1.19, 95%CI 0.72-1.97). Anatomic sites of infection that were more common in RA-LD included pulmonary, skin and soft tissue, and ear, nose and throat; RA-LD was associated with various pathogen types: virus, bacteria, fungus, and mycobacteria. Specific pathogens with higher frequency in RA-LD cases, particularly among RA-BR, included influenza virus, respiratory syncytial virus, Staphylococcus, Pseudomonas, and nontuberculous mycobacteria. RA-LD, particularly RA-ILD, is associated with a significant increased risk of serious infection across anatomic sites and diverse pathogen types. RA-BR is associated with increased pulmonary infections. Prospective studies and trials are needed to clarify optimal approaches to treat patients with RA-LD and reduce infection risk.