Evaluating the role of lung ultrasound in the diagnosis of rheumatoid arthritis-interstitial lung disease

The involvement of the pulmonary parenchyma in rheumatoid arthritis (RA), characterized by the presence of interstitial lung disease (RA-ILD), represents one of the most common and potentially severe extra-articular manifestations of the disease. High-resolution computed tomography (HRCT) of the chest is considered the gold standard diagnostic technique; however, its reliance on ionizing radiation and the limited availability of imaging equipment make it challenging to perform repeatedly. Over the past decade, lung ultrasound (LUS) has emerged as a noninvasive and easily repeatable technique for detecting the presence of RA-ILD. This narrative review summarizes the currently available evidence on the use of LUS in RA-ILD. It begins by defining the elementary lesions indicative of pulmonary involvement (B-lines and pleural irregularities) and provides an overview of LUS application in other connective tissue disease-associated interstitial lung diseases (CTD-ILDs). Current evidence suggests a promising role for LUS in the screening of RA-ILD, primarily based on the quantification of B-lines. Initially, a threshold of 10 B-lines was proposed, which has recently been lowered to 5, demonstrating good sensitivity and specificity in detecting RA-ILD. Future directions should focus on the role of pleural irregularities and the further standardization of the technique.