A Lung Ultrasound Score for Assessing Connective Tissue Disease‐Related Interstitial Lung Disease: Performance and Comparison With Computed Tomography Quantification

Background and Objective The role of lung ultrasound's (LUS) in diagnosing and assessing connective tissue disease (CTD)‐related interstitial lung disease (ILD) remains controversial. We aimed to evaluate the diagnostic performance of a quantitative LUS score and the correlations between LUS scores and quantitative computed tomography (QCT) parameters in patients with CTD‐ILD. Methods This prospective study included individuals with CTD and clinical suspicion of ILD attending our hospital between December 2023 and November 2024. LUS was performed using a 14 intercostal scanning protocol; high‐resolution computed tomography (HRCT) was analysed using artificial intelligence‐based QCT software. Participants underwent pulmonary function tests (PFTs) and completed the King's Brief Interstitial Lung Disease (KBILD) questionnaire. We analysed the LUS score's diagnostic efficacy and its correlations with QCT findings, PFT results, and KBILD scores. Results Among 206 patients with CTD enrolled, 145, 30, and 31 were categorised into ILD, preclinical ILD, and non‐ILD groups, respectively. Patients with ILD exhibited higher LUS scores and QCT parameters but lower PFT results and KBILD scores than those without ILD or with preclinical ILD. At cutoff scores of 5.5 and 14.5, LUS distinguished non‐ILD from preclinical ILD and ILD with sensitivities of 93.1% and 93.8% (specificities: 83.9% and 86.9%, respectively). LUS scores correlated positively with all QCT parameters, particularly fibrosis extent ( r = 0.784; p < 0.001). Median LUS scores differed significantly among PFT and HRCT‐defined ILD extent groups. Conclusion LUS facilitates early diagnosis of CTD‐ILD, and quantitative LUS score correlates with QCT‐defined ILD extent. Trial Registration Chinese Clinical Trial Registry (registration number ChiCTR2400080909)