Frequency of Interstitial Lung Disease in Rheumatoid Arthritis Patients: A Hospital-Based Study

Among various extra-articular manifestations of rheumatoid arthritis (RA), interstitial lung disease (ILD) is the most frequent and concerning manifestation. The reported frequency of RA-associated ILD (RA-ILD) varies in the literature. The objective of the present study was to determine the frequency of ILD in RA patients at a teaching hospital in Rawalpindi.

175 male and female patients between 18-70 years were enrolled in the study from January 21, 2022, till July 24, 2022. Patients diagnosed with RA were screened for the concomitant presence of ILD (increased pulmonary markings on chest X-rays and total lung capacity ≤ 80%, predicted on pulmonary function tests). In addition, the frequency of RA-ILD was noted and compared across various subgroups of patients based on age, gender, and disease duration.

The mean age of the patients was 45.3 ± 11.5 years. The male-to-female ratio was 1:3.1. The mean disease duration was 6.2 ± 3.5 years at the time of presentation. A total of 118 (67.4%) patients were diagnosed with RA-ILD. The frequency of RA-ILD was significantly higher among patients with a prolonged duration of disease, < 5 years vs. ≥ 5 years (59.1% vs. 75.9%; p-value=0.018). Among 118 patients with RA-ILD, usual interstitial pneumonia (UIP) was the most frequent pattern and was noted in 74 (62.7%) patients, followed by nonspecific interstitial pneumonitis (NSIP), which was noted in 44 (37.3%) patients. When compared, there was no statistically significant difference in the frequency of high-resolution CT (HRCT) pattern of RA-ILD across various subgroups of patients based on age (p-value=0.969), gender (p-value=0.934), and duration of disease (p-value=0.881).

In the present study, a substantial proportion of RA patients suffered RA-ILD, which warrants routine screening of these patients for undiagnosed pulmonary involvement so that timely identification and anticipated management may improve the outcome of such cases in future clinical practice.