Predictive factors of mortality in rheumatoid arthritis-associated interstitial lung disease analysed by modified HRCT classification of idiopathic pulmonary fibrosis according to the 2018 ATS/ERS/JRS/ALAT criteria

Background: Interstitial lung disease (ILD) is associated with high morbidity and mortality in rheumatoid arthritis (RA). Although usual interstitial pneumonia (UIP) pattern was reported as a poor prognostic factor, in clinical practice, we often cannot classify high-resolution computed tomography (HRCT) patterns specifically as UIP or nonspecific interstitial pneumonia (NSIP). This study of RA-ILD aimed to elucidate prognosis by using our modified HRCT pattern classification according to the latest guideline on idiopathic pulmonary fibrosis (IPF). Methods: We analysed the medical records of 96 consecutive patients diagnosed as having RA-ILD. The modified HRCT classifications were defined as definite UIP, probable UIP, indeterminate for UIP (i.e., early UIP or NSIP/UIP), NSIP, organizing pneumonia (OP), NSIP+OP, and unclassifiable. Predictors of prognosis were determined using Cox regression models. Results: Our RA-ILD cohort included definite UIP (21%), probable UIP (20%), indeterminate for UIP (30%) including NSIP/UIP (27%), alternative diagnosis (29%) including NSIP (14%), and other patterns. Interrater agreement for HRCT pattern was good (κ =0.75). Multivariate analysis showed that older age, history of acute exacerbation, and radiological honeycombing were negative prognostic factors of mortality. Conclusions: NSIP/UIP pattern of indeterminate for UIP was the major pattern in RA-ILD. Although classifications of HRCT patterns were not related to survival, the presence of radiological honeycombing could be a useful predictor of poor prognosis, and acute exacerbation of ILD can seriously impact patient survival regardless of the presence of a UIP or indeterminate for UIP pattern. Our modified HRCT classification based on the latest IPF guideline might be useful to assess appropriate strategies of diagnosis in future RA-ILD studies, and radiological honeycombing could better predict poor prognosis rather than HRCT pattern.