POS0555 THE NATURAL COURSE OF RHEUMATOID ARTHRITIS-ASSOCIATED INTERSTITIAL LUNG DISEASE FOCUSING ON LUNG PHYSIOLOGY: A PROSPECTIVE OBSERVATIONAL COHORT STUDY (PART 1)
Authors: S. H. Chang, J. S. Lee, J. S. Lee, C. H. Park, M. U. Kim, Y. J. Ha, E. H. Kang, Y. A. Lee, Y. Park, J. Y. Choe, E. Y. Lee
Journal: Annals of the Rheumatic Diseases (2021)

Background: Interstitial lung disease (ILD) is a severe extra-articular manifestation of rheumatoid arthritis (RA). However, there are few prospective studies for the natural course of lung physiology in most patients with RA-ILD. Objectives: To assess the natural course of lung physiology of RA-ILD and the relation between arthritis activity and pulmonary physiology in patients with RA-ILD. Methods: The KOrean Rheumatoid Arthritis ILd (KORAIL) cohort is the prospective observational cohort and aims to investigate the natural course of RAILD. Based on either 1987 or 2020 ACR criteria, patients diagnosed with RA and ILD based on CT scan were recruited from six tertiary medical hospitals in Korea since January 2015. RA disease activity was assessed using swollen and tender joint count by treating physician, inflammatory markers including CRP and ESR, and patient’s global assessment annually. Pulmonary function tests (PFT), including FVC, FEV1, DLCO, and chest CT scan, were conducted annually. Results: We analyzed 163 patients at baseline (V1), 141 at 1-year (V2), 122 at 2-year (V3), and 88 at 3-year follow-up (V4). The mean (±SD) duration since RA diagnosis and since ILD diagnosis was 7.6±8.0 and 2.7±3.1 years, respectively. The female to male ratio was about 2:1, and 58.9% of patients (n=96) were 65 years old or older. Only two patients were negative for RF and anti-CCP; 98.7% of patients (n=161/163) were positive for RF (n=143, 87.7%) or anti-CCP antibody (n=154, 94.5%). At enrollment, one-hundred-nine patients (66.9%) had FVC ≥80 % of predicted. Twenty-five patients (15.3%) showed FEV1/FVC≥0.7, of which seventeen patients, only ten percent of a total cohort (10.4%), had FVC ≥80% of predicted, which corresponds to the obstructive pattern. Proportion of patients showed a ≥10-point decline from the enrollment in FVC of the predicted value were around 10% at every year (Table 1). The proportion of patients with a relative decline of ≥10% from the enrollment in FVC predicted was increased every year because of cumulation. The proportion of patients with a relative decline of ≥10% from the previous visit in FVC predicted was also around 10-15% every year. Proportions of patients with 55% or more DLco % pred. has been decreased annually; 78.5% (n=128/158) at V1, 72.9% (n=105/139) at V2, 68.7% (n=90/117) at V3, and 56.6% (n=56/85) at V4. Patients with a relative decline of ≥10% from the enrollment in DLco predicted was 38 (27.5 %) at V2 and 37 (31.9%) at V3. Patients with a relative decline of ≥10% from the previous visit in DLco predicted was 29 (25.2%) at V3. Of note, thirty patients (21.7%) showed a relative 10% or more increase from enrollment in DLco predicted at V2, and so did 30 patients (25.9%) at V3. Table 1. The analysis of forced vital capacity (FVC) in KORIL cohort V1 (enrollment) V2 (1-year) V3 (2-year) V4 (3-year) FVC (mL), mean±SD 2549.5 ± 743.3 2479.5±764.4 2435.8 ± 742.8 2405.7 ± 731.2 FVC % of predicted, mean±SD 84.70 ± 16.74 84.7±18.1 84.3 ± 17.6 83.1 ± 19.1 Rate of FVC decline, mL·year -1 (95% CI) - -14 (-49, 21) -62 (-104, -21) - A 10-point decline from V1 in predicted FVC value, n (%) - 10 (7.1) 16 (13.3) 8 (9.4) Relative decline of 10% from V1 in predicted FVC value, n (%) - 17 (12.1) 23 (18.9) 17 (19.3) Relative decline of 10% from the previous visit in predicted FVC value, n (%) - 17 (12.1) 17 (14.2) 13 (15.3) Conclusion: Annually, about 10-15% of patients experience a relative ≥10% decline from the previous visit in FVC predicted value in RA-ILD. Acknowledgements: This work was supported by the Korea Health Technology R&amp;D Project through the Korea Health Industry Development Institute, funded by the Ministry of Health and Welfare, Republic of Korea (grant no.HI14C1277). Disclosure of Interests: None declared