© 2021 Kamonwon Ienghong, Takaaki Suzuki, Ismet Celebi, Vajarabhongsa Bhudhisawasdi, Somsak Tiamkao, Dhanu Gaysonsiri, Korakot Apiratwarakul.BACKGROUND: B-line artifacts (BLAs) play an important role in identifying lung pathology. They may indicate different diseases. However, the diagnostic study of BLA as applied to emergency patients has not been well studied. AIM: The aim of this study was to determine the diagnostic accuracy of BLA in various conditions. METHODS: This was a retrospective observational study of emergency patients who had received lung ultrasound at Srinagarind Hospital’s Emergency Department throughout January 2020–December 2020. Ultrasound artifacts were recorded. Ultrasonography findings were correlated with final diagnosis. Sensitivity and specificity were also calculated. RESULTS: A total of 105 patients were evaluated. The most prevalent condition which BLA found in this study was pulmonary edema (44.12%) with 88.24% sensitivity and 46.48% specificity. BLA also indicated pneumonia with 66.67% sensitivity and 35.71% specificity. Diffuse BLA indicated pulmonary edema with 70% sensitivity and 70.42% specificity. Focal BLA indicated pneumonia with 28.57% sensitivity and 76.19% specificity. CONCLUSIONS: The sensitivity of BLA for pulmonary edema and pneumonia diagnosis in this study was of moderate to good sensitivity, but low specificity. BLA may become crucial in the diagnosis of lung pathology in the emergency department.