Quantitative CT Scan Analysis in Rheumatoid Arthritis-Related Interstitial Lung Disease

Background: Quantitative CT imaging may be a useful predictor of outcome in rheumatoid arthritis-related interstitial lung disease (RA-ILD).

Research question: What is the utility of deep learning-based lung fibrosis quantitation on CT imaging in assessing disease severity, predicting mortality, and identifying progression in RA-ILD?.

Study design and methods: CT scans on a primary cohort of 289 patients and a validation cohort of 50 individuals with RA-ILD were assessed quantitatively by using the data-driven texture analysis (DTA) method. We examined associations between quantitative scores for extent of lung fibrosis and pulmonary function and survival.

Results: DTA fibrosis score at baseline showed moderate negative correlation with FVC percent predicted (primary cohort rho = -0.55; validation cohort rho = -0.50; both, P < .001), and diffusing capacity for carbon monoxide percent predicted (primary cohort rho = -0.67; validation cohort rho = -0.65; both, P < .001). Longitudinal change in DTA fibrosis score was associated with changes in FVC and diffusing capacity for carbon monoxide in the primary cohort (rho = -0.46 and rho = -0.43, respectively; both, P < .001). Cox multivariable models adjusted for potentially influential variables showed that the baseline DTA fibrosis score was significantly associated with mortality risk (primary cohort hazard ratio [HR], 1.04 [95% CI, 1.03-1.05; P < .001]; validation cohort HR, 1.06 [95% CI, 1.01-1.11; P = .026]). In the primary cohort, the increase in DTA fibrosis score on sequential scans was associated with increased risk of mortality (HR, 1.04; 95% CI, 1.01-1.06; P = .003) independent of baseline DTA extent.

Interpretation: In two cohorts of patients with RA-ILD, quantitative assessment of lung fibrosis on CT imaging was associated with worse lung function at baseline and risk of mortality. Increase in DTA-derived lung fibrosis score on sequential scans was associated with subsequent risk of mortality. Quantitative CT imaging should be considered for use as a clinical and research outcome assessment tool in RA-ILD.