Background: Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease that is commonly associated with extra-articular manifestations. Pulmonary disease is frequently encountered, which causes serious morbidity and increases mortality. Among the pulmonary manifestations, interstitial lung disease (ILD) is the most common. We aimed to analyse the frequency and clinical characteristics of a cohort of patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD); describe the radiological features of ILD; identify predictive factors for developing ILD; and evaluate the impact of ILD on patient survival.
Materials and methods: This retrospective study included all patients with RA who attended the rheumatology clinic of Kuala Lumpur Hospital from 2018 to 2021. RA-ILD was identified from high-resolution computed tomography (HRCT) thorax images evaluated by two thoracic radiologists. Descriptive and logistic regression analyses were conducted using SPSS version 26.0.
Results: Of the 732 patients with RA, 7.4% (54) had ILD. Univariate analysis identified Indian ethnicity, rheumatoid factor (RF) positivity, anti-cyclic citrullinated peptide antibody titre, and diabetes mellitus as risk factors for developing ILD. Multivariable logistic regression showed that RA-ILD was positively associated with female gender [Adjusted odds ratio (aOR)=3.40 (95% confidence interval (CI): 1.04, 11.17)], Indian ethnicity [aOR=2.03 (95% CI: 1.16, 3.57)], and positive RF [aOR=2.39 (95% CI: 1.18, 4.87)]. Nonspecific interstitial pneumonia (NSIP) was the predominant HRCT pattern. Majority of patients had limited disease (<20% of lung involvement) and good functional exercise capacity. There was significant improvement (p<0.05) in mean forced vital capacity (FVC) following treatment with immunosuppressive agents. No mortality occurred throughout the median follow-up period of 3.2 years.
Conclusion: RA patients of Indian ethnicity had an increased risk for developing ILD, suggesting that genetics play a crucial role. Other independent predictors were female gender and RF positivity. The pattern of HRCT thorax and extent of lung involvement influenced prognosis and survival of patients with RA-ILD.