Computed tomography-based quantitative scoring system for rheumatoid arthritis–associated interstitial lung disease: a retrospective diagnostic accuracy study for progressive fibrosis detection

This study demonstrates that quantitative methods (Method 1 [- 700 to - 200 HU] and Method 2 [- 800 to - 500 HU]) play a significant role in assessing the severity of RA-associated ILD (RA-ILD). Both methods showed significant correlations with pulmonary function tests (DLCO [r₁ = - 0.338, p₁ = 0.025; r₂ = - 0.452, p₂ = 0.002] and TLC [r₁ = - 0.567, p₁ < 0.001; r₂ = - 0.576, p₂ < 0.001), with Method 1 (AUC_ILD = 0.945 and AUC_MCRD = 0.911) demonstrating superior performance in distinguishing between limited and extensive ILD. Our findings suggest that Hounsfield unit threshold-based quantitative CT analysis may serve as a more objective and reproducible alternative to semiquantitative systems (e.g., Goh score) in the standard evaluation of RA-ILD. Specifically, Method 1 may enable early detection of progression by mechanism, e.g., "tracking subtle density changes." However, further validation in multicenter prospective cohorts is needed to address limitations such as bias. Key Points • Interobserver and intraobserver variability poses a significant challenge in the objective assessment of rheumatoid arthritis-associated interstitial lung disease. • User independent quantitative methods can be used instead of user-dependent semiquantitative methods in assessing rheumatoid arthritis-associated interstitial lung disease. • Quantitative computed tomography analysis enables precise stratification of disease severity in rheumatoid arthritis-associated interstitial lung disease, distinguishing limited interstitial lung disease from extensive interstitial lung disease, which has a poor prognosis.