Integrated Use of Lung Ultrasound and Chest X-Ray in the Detection of Interstitial Lung Disease

BACKGROUND: Current data have shown that lung ultrasound (LUS) may be useful in the detection of interstitial lung disease (ILD) by the evaluation of B-lines, the sonographic marker of pulmonary interstitial syndrome. Nevertheless, no prospective study has compared LUS to chest X-ray (CXR) for ILD assessment, and there is no general agreement on the specific echographic diagnostic criteria for defining ILD. OBJECTIVES: The aims of this study were (1) to compare the accuracy of LUS and CXR in the detection of ILD using high-resolution CT (HRCT) as the gold standard and (2) to compare the accuracy of different echographic diagnostic criteria for ILD diagnosis. METHODS: LUS was performed on 104 patients undergoing HRCT for suspected ILD. In 49 patients, a CXR scan performed within 3 months of HRCT was analyzed. ILD was defined as the presence of ≥5 B-lines in ≥3 chest areas. A total B-line score (TBLS) was also calculated, as in previous studies. The observers evaluating LUS and CXR were blinded to the HRCT results and clinical data. RESULTS: On HRCT, ILD was assessed in 50 patients. CXR was specific (91%; 95% CI 80-100) but not sensitive (48%; 95% CI 28-67). Conversely, LUS showed high sensitivity (92%; 95% CI 84-99) and low specificity (79%; 95% CI 69-90). Using a TBLS, sensitivity did not change, while specificity decreased. CONCLUSIONS: LUS could be a sensitive tool for ILD detection. CXR and LUS have different but complementary features, and their combined use could reduce the need for HRCT. The use of different diagnostic criteria for defining ILD does not affect sensitivity but influences specificity.