Diagnostic Validity of Lung Ultrasonogram in Comparison with High-Resolution Computed Tomography in Interstitial Lung Disease Associated with Connective Tissue Disease

Background: Lung ultrasonography (LUS) may be a useful tool in identifying interstitial lung disease (ILD) in patients with Connective tissue disorder (CTD). The aim of the current study was to determine the diagnostic validity of LUS findings in comparison with high-resolution computed tomography (HRCT) in CTD-ILD and also determine the correlation between forced vital capacity (FVC) and 6-min walk test (6MWT) to LUS. Patients and Methods: Patients with connective tissue disorder and ILD diagnosed by HRCT were included and evaluated by physical examination, LUS, spirometry, and 6MWT. Results: Of 41 patients included, 38 (92.7%) were females. The mean age was 49.7 years. Systemic sclerosis was the most common diagnosis in 25 (61%) patients. LUS score was calculated as the total number of B-lines counted in all zones. The mean score was 20.83. B-line score showed a negative correlation with 6MWT distance (R = -0.501, P = 0.001) and FVC (R = -0.434, P = 0.005). There was a strong positive correlation between LUS and HRCT scores (R = 0.878, P = 0.0001). A LUS score of 39.5 or above has 83% sensitivity and 100% specificity (Youden index of 0.83, P = 0.001) for predicting a Class V HRCT pattern. Conclusions: There was a significant correlation between ILD with reticular pattern and honeycombing on HRCT and higher LUS B-line scores. LUS B-line scores also correlated significantly with functional parameters such as lower FVC values and 6MWT distance.