Rheumatoid arthritis associated interstitial lung disease: diagnostic accuracy of lung ultrasound compared to chest high resolution computed tomography.

Introduction: Interstitial lung disease (ILD) affects up to 60% of patients with rheumatoid arthritis (RA). Chest high-resolution computed tomography (HRCT) remains the gold standard for diagnosis; however, it involves radiation exposure. Lung ultrasound (LUS) is a safe and accessible tool, but it has not yet been validated for ILD diagnosis in RA. Methods: We conducted a prospective, single-center, cross-sectional study including patients followed for RA. Exclusion criteria were pregnancy, history of heart failure, acute cardiac decompensation, respiratory symptoms within the last 3 months, and pneumonia within the past month. All included patients underwent both LUS and chest HRCT. The diagnostic performance of LUS was assessed using HRCT as the reference standard. Results: A total of 73 patients were included (18 men and 55 women), with a mean age of 55 ± 12 years. The mean Disease Activity Score (DAS28-ESR) was 3.47 ± 1.40. Chest HRCT identified ILD in 28.8% of patients. According to the semi-quantitative ultrasound score, interstitial involvement was detected in 21.9% of patients. The sensitivity of LUS was 59.1%, and the specificity was 94.1%. Receiver operating characteristic (ROC) curve analysis showed an area under the curve (AUC) of 0.813. The optimal cutoff was 5 B-lines, yielding a sensitivity of 63.6% and a specificity of 94.1%. Discussion: LUS demonstrated good diagnostic performance for ILD detection in RA patients, with high specificity. These findings suggest that LUS may represent a useful screening tool to identify patients requiring further evaluation with HRCT.