Risk Factors Associated with Interstitial Lung Disease in Rheumatoid Arthritis: A Monocentric Clinical and Serological Assessment

Abstract Interstitial lung disease (ILD) is a severe extra-articular manifestation of rheumatoid arthritis (RA). This study identified risk factors and developed a predictive model for RA-ILD in 208 RA patients from the Second Affiliated Hospital of Soochow University (2010–2023). ILD was confirmed via high-resolution computed tomography (HRCT). Logistic regression and ROC curve analyses determined optimal biomarker thresholds: rheumatoid factor (RF) > 352.5 IU/mL, anti-CCP antibodies > 43.25 IU/mL, complement C3 < 0.765 g/L, C4 < 0.1935 g/L, and TNF-α > 1.7295 pg/mL. Univariate analysis linked male gender, smoking, elevated RF/anti-CCP, low C3/C4, high TNF-α, and reduced biologic therapy to ILD (all P < 0.05). Multivariate analysis confirmed C3, TNF-α, and biologic therapy as independent predictors (P < 0.05). The nomogram demonstrated strong discrimination (C-index 0.829, 95% CI 0.756–0.902). RA-ILD exhibits distinct features (male predominance, smoking, dysregulated immunity), while biologic therapy may be protective. This model aids early risk stratification and clinical decision-making.