Lung ultrasound B-lines in systemic sclerosis: cut-off values and methodological indications for interstitial lung disease screening

Objectives: Lung ultrasound (LUS), through assessment of B-lines and pleural line alterations, is able to evaluate interstitial lung disease (ILD), a frequent complication of SSc. Different scanning schemes and counting methods have been proposed but no clear cut-off values have been indicated for screening. We aimed to evaluate the accuracy of different LUS methodological approaches to detect ILD compared with high-resolution CT (HRCT) as the gold standard. Methods: Sixty-nine SSc patients underwent LUS and chest HRCT on the same day. Both exams were scored by expert readers. The accuracy of different scanning schemes and counting methods was assessed and clinical and functional data were compared with imaging findings. Results: B-lines were more numerous in patients with the diffuse skin subset and Scl70 autoantibody positivity. The number of B-lines correlated with the Scleroderma Lung Study (SLS) I HRCT score (R = 0.754, P < 0.0001). A total of >10 B-lines on the whole chest or >1 B-line on the postero-basal chest showed 97% sensitivity for detecting even very early ILD signs (corresponding to an SLS I score of 1). Sensitivity increased to 100% when pleural line alterations were included in the analysis. Conclusions: LUS has a very high sensitivity in detecting SSc-related ILD. A cut-off value of >10 B-lines on the whole chest or >1 B-line on the postero-basal chest can be used for the screening of SSc-ILD. Assessing only the postero-basal chest seems to be mostly effective, combining high sensitivity with a less time-consuming approach.