Point-of-care lung ultrasonography for early identification of mild COVID-19: a prospective cohort of outpatients in a Swiss screening center

Background Early identification of SARS-CoV-2 infection is important to guide quarantine and reduce transmission. This study evaluates the diagnostic performance of lung ultrasound (LUS), an affordable, consumable-free point-of-care tool, for COVID-19 screening. Methods This prospective observational cohort included adults presenting with cough and/or dyspnea at a SARS-CoV-2 screening center of Lausanne University Hospital between March 31 st and May 8 th , 2020. Investigators recorded standardized LUS images and videos in 10 lung zones per subject. Two blinded independent experts reviewed LUS recording and classified abnormal findings according to pre-specified criteria to investigate their predictive value to diagnose SARS-CoV-2 infection according to PCR on nasopharyngeal swabs (COVID pos vs COVID neg ). We finally combined LUS and clinical findings to derive a multivariate logistic regression diagnostic score. Results Of 134 included patients, 23% (n=30/134) were COVID pos and 77% (n=103/134) were COVID neg ; 85%, (n=114/134) cases were previously healthy healthcare workers presenting within 2 to 5 days of symptom onset (IQR). Abnormal LUS findings were significantly more frequent in COVID pos compared to COVID neg (45% versus 26%, p=0.045) and mostly consisted of focal pathologic B-lines. Combining LUS findings in a multivariate logistic regression score had an area under the receiver-operating curve of 63.9% to detect COVID-19, but improved to 84.5% with the addition of clinical features Conclusions COVID pos patients are significantly more likely to have lung pathology by LUS. Our findings have potential diagnostic value for COVID-19 at the point of care. Combination of clinical and LUS features showed promising results, which need confirmation in a larger study population. What is already known on the subject Lung ultrasonography (LUS) is a consumable-free, easy-to-use, portable, non-radiating and non-invasive screening tool that can be performed at the bedside: its diagnostic performance for pneumonia has been established. Recent studies conducted in emergency department showed a correlation between LUS findings and COVID-19 diagnosis. What the study ads This is the first study assessing the diagnostic performance of LUS for COVID-19 in outpatients with mild acute respiratory tract infection. Mild COVID-19 patients are more likely to have lung pathology by LUS compared with COVID-19 negative. Combination of clinical and LUS features showed promising results with a potential diagnostic value for COVID-19 at the point of care.