Lung ultrasound is a promising screening tool to rule out interstitial lung disease in patients with rheumatoid arthritis.

Background and objective: It is still controversial how to screen for interstitial lung disease (ILD) in patients with rheumatoid arthritis (RA). We aimed to evaluate the performance of lung ultrasound (LUS) as a screening tool for RA-ILD and to compare it with the performance of chest auscultation, chest x-ray and pulmonary function tests (PFTs).

Methods: Cross-sectional study of consecutive RA patients evaluated at a Rheumatology Clinic in Buenos Aires between January and December 2022. High-resolution computed tomography (HRCT) was the gold standard for diagnosing ILD and was performed within 30 days of the LUS, chest x-ray and PFTs. Investigators were blinded to HRCT results and patients' clinical data. LUS was performed by exploring 14 areas and was considered positive when the sum of B lines was ≥5. Performance for the diagnosis of ILD was reported for each diagnostic test.

Results: One hundred and six patients were included; 87 (82%) were women. Median age was 60.9 (±9.5) years-old. A total of 32 (30.2%, 95% CI: 21.6%-39.9%) had ILD. The sensitivity and negative predictive value of LUS were 90.6% (95% CI 75.0%-98.0%) and 94.7% (95% CI 85.4%-98.9%), respectively. LUS performance was superior to that of the other evaluated diagnostic tests for screening ILD.

Conclusions: Given that the US is a low-cost point-of-care tool with a high negative predictive value, it is emerging as a valuable tool for ruling out ILD in patients with RA.