Rheumatoid arthritis-associated interstitial lung disease in countries across the world

We aimed to describe the incidence of RA-ILD in various countries worldwide, and to explore its association with RA disease activity.

In 5 countries, data on RA-ILD (clinical diagnosis based on chest X-ray or CT) were collected RA patients of two observational databases (METEOR, EAC). We investigated a possible association between disease activity over time and RA-ILD.

16,663 patients with RA with variable disease duration were evaluated. At the first visit recorded in the database, 1/1077 (0.09 %) patients from The Netherlands, 63/11,787 (0.53 %) from India, 8/629 (1.27 %) from South Africa, 6/424 (1.42 %) from Mexico and 17/2728 (0.62 %) from Colombia had an RA-ILD diagnosis. The incidence rate of RA-ILD in patients with newly diagnosed RA was 3.8 (95 % CI 1.6 to 9.1) per 1000 patient years in The Netherlands, 1.6 (95 % CI 1.0 to 2.5) in India and 6.6 (95 % CI 2.5-17.5) in South Africa. The OR for RA-ILD development, per point increase in DAS28 over time was 1.19 (95 % CI 0.34 to 4.22). Disease activity after the RA-ILD diagnosis or a matched timepoint was statistically significantly higher in patients with RA-ILD than in controls (β 0.56 (95 % CI 0.18 to 0.93). There were no clear differences in DMARD use between the two groups.

Despite slight differences in RA-ILD prevalence and incidence between countries, the incidence of RA-ILD in daily practice is low in our RA population from different continents. Patients with RA-ILD had a higher disease activity than patients without RA-ILD, and were more often ACPA positive and/or (former) smokers.