Objective. Interstitial lung disease (ILD) is a common pulmonary manifestation of rheumatoid arthritis (RA), and an important cause of morbidity and mortality in RA. We compared demographic and clinical characteristics of usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) patterns in RA patients and determined the prognostic factors that influence the survival of RA-ILD patients.
Methods. 51 enrolled RA patients (male n=21, female n=30) with ILD underwent HRCT. We categorized ILD into two groups, as the UIP pattern and the NSIP pattern, using HRCT. HRCT scans were scored to investigate the extent of the ILD. We divided the extent of the interstitial lung disease into 4 groups 1∼14%, 15∼19%, 20∼24%, ＞25%.
Results. There were no significant differences between the UIP and NSIP pattern in the clinical characteristics, except for age at the time of the study (RA-NSIP pattern vs RA-UIP pattern 62.3±11.7 vs 68.2±8.4, p=0.042). There were no significant differences in survival time between the RA-UIP and RA-NSIP pattern (Log rank p=0.985). The extent of ILD on chest HRCT was significantly associated with mortality (HR=1.044, 95% CI 1.019∼1.069) and patients that were diagnosed with ILD at an older age (HR=1.109, 95% CI 1.024∼1.200) were associated with a worse prognosis. Comparing four groups divided by the extent of the lung disease, there were significant differences in survival estimates (Log-rank p-value＜0.001) based on an ILD extent of 15%.
Conclusion. Our study reveals that the extent of ILD on chest HRCT was found to be significantly associated with poor prognosis of RA-ILD patients.

Keywords: Rheumatoid arthritis, Interstitial lung disease, High resolution computed tomography, Lung disease extent, Prognosis