Advances in the validation of lung ultrasound for the detection of interstitial lung disease associated with rheumatoid arthritis

Interstitial lung disease (ILD) is one of the most important extra-articular manifestations of rheumatoid arthritis (RA) due to its associated significant mortality. The availability of pharmacological treatments capable of slowing its progression, especially when initiated early, makes early diagnosis an essential part of its management. The low sensitivity of chest X-ray or lung function tests to identify RA-ILD in the early stages of the disease, together with the cost, accessibility, and ionizing radiation limitations of high-resolution computed tomography (HRCT), especially when serial screening or follow-up studies are required, has prompted the study of lung ultrasound (LUS) as an additional aid for the screening, diagnosis, and/or follow-up of RA-ILD. Based on the safety, low cost, and accessibility of LUS, and the encouraging results of research into this technique in ILD associated with systemic sclerosis, progress has been made in its validation process with research addressing aspects such as its accuracy, feasibility, and reliability. Negative predictive value and sensitivity values exceeding 80–90% have been reported, suggesting its potential utility. Feasibility has been suggested since LUS scan can be performed in less than 10 minutes, and intra- and inter-observer or examiner reliability shows values in the good to excellent range. However, there are still aspects that require further investigation, such as the standardization of the LUS scanning protocol or the requirements to ensure an effective learning curve before applying the technique in clinical practice. It is necessary to recognize the inherent limitations of LUS and understand that it should be considered a tool to aid in the early identification of patients who require HRCT, which is currently the diagnostic gold standard.