Correlation between Lung and Joint Involvement in Patients with Rheumatoid Arthritis and Interstitial Lung Disease: A Cross-Sectional Study.

BACKGROUND: Rheumatoid arthritis (RA) can affect the lungs in different manners, with interstitial lung disease (ILD) as the most serious manifestation. Although lung and joint compromise could be thought to evolve in parallel, there are data suggesting the opposite. In this study, we evaluated the relationship between lung and joint involvement in RA ILD.

METHODS: An observational cross-sectional study of RA ILD patients evaluated from January 2015 to February 2017. Joint disease assessment included number of tender and swollen joints, patient's global assessment of disease activity, erythrocyte sedimentation rate (ESR) or C-reactive protein, and disease activity score (DAS28). Lung disease assessment included forced vital capacity, diffusion capacity (DLCO), and Goh high-resolution computed tomography (HRCT) score for total extent, ground glass, and reticular pattern. We studied the correlation between both components of the disease.

RESULTS: We included 46 patients, 14 (30.4%) men, with a mean (SD) of the age of 59.9 years (11.89). 12 (26.09) patients were in remission or had low disease activity measured with DAS28. The HRCT showed usual interstitial pneumonia (UIP) pattern in 10 (21.7%), possible UIP in 18 (39.1%), and inconsistent with UIP in 18 (39.1%). We found a good correlation between the ESR and the ground glass score in the HRCT (r = 0.39; p = 0.03). However, we found no correlation between lung function tests or HRCT scores and the other components of the DAS28.

CONCLUSIONS: We only found a good correlation between ESR and ground glass score. It is possible that different pathways of the immune response mediate damage in lungs and joints.