Lung ultrasound for the assessment of interstitial lung disease in systemic sclerosis: clinical correlations and prognostic implications.

Background: A high percentage of systemic sclerosis (SSc) patients develop interstitial lung disease (ILD) during the course of the disease. Promising data have recently shown that lung ultrasound (LUS) is able to assess ILD by the evaluation of B-lines, the sonographic marker of pulmonary interstitial syndrome. Aim: To confirm the accuracy of LUS B-lines to detect ILD, compared to the gold-standard high resolution computed tomography (HRCT), in a large number of SSc patients, and to establish their clinical correlates and prognostic implications. Methods: Two hundred and eight consecutive SSc patients (189 females, mean age 51±15 years) enrolled at three different Rheumatology Departments underwent LUS examination and chest HRCT. All available clinical and functional data were compared to imaging findings. Patients were followed-up after enrolment to establish the prognostic role of LUS. Results: B-lines were more numerous in patients with the diffuse form of the disease (83±77 vs 37±59, p<0.001) and with Scl-70 autoantibodies positivity (65±69 vs 35±57, p<0.01). LUS showed a sensitivity of 99.3% and a specificity of 72.9% to detect ILD compared to HRCT. At multivariable analysis, a number of B-lines > 35 was an independent predictor of worsening pulmonary involvement (hazard ratio [HR] 4.2; 95 % confidence interval [CI] 1.31–13.44), with additional value over Scl-70 positivity at stepwise analysis (p<0.01). Conclusions: Lung ultrasound evaluation of B-lines has a very high sensitivity in detecting ILD signs compared to HRCT, and carries a strong prognostic value. The use of LUS as a screening tool for ILD seems feasible to guide further investigation with HRCT.