Interstitial lung disease in a single center inception cohort of early rheumatoid arthritis patients

Introduction: Interstitial lung disease (ILD) is a serious complication to rheumatoid arthritis (RA) and increases mortality. The frequency of interstitial lung disease among patients with early rheumatoid arthritis is insufficiently studied. Objectives: The aim of this study was to characterize the frequency of ILD among patients newly diagnosed with early RA in an inception cohort. Methods: The study included DMARD naive patients consecutively diagnosed with RA according to ACR/EULAR criteria 2010. Enrolment took place between October 2009 and November 2012. Within the first six months after diagnosis, a subgroup of patients underwent pulmonary function tests with spirometry and measurement of total lung capacity, residual volume and diffusion capacity of carbon monoxide. The remaining patients were referred for pulmonary follow up on clinical indication only. Results: The entire study population included 230 patients with early RA, 65 % were anti-CCP positive and 60% were IgM RF-positive. Mean age was 59.5 years and 41% were male. Seventy-one patients were selected for pulmonary function testing. None of these patients had signs of RA-ILD based on pulmonary function tests, but obstructive lung disease with emphysema was revealed in ten cases. In the entire cohort, a total of six patients had been diagnosed with interstitial lung disease, one patient had unspecific fibrosis on HRCT, three had NSIP and two had UIP pattern. Two of these patients had been diagnosed with ILD several years prior to the RA-diagnosis. Conclusion: Screening with pulmonary function tests revealed very few cases of ILD in early RA. However, follow up of this cohort may be able to identify risk factors of RA-ILD.