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

Schaad, S.; Brahier, T.; Hartley, M.-A.; Cordonnier, J.-B.; Bosso, L.; Espejo, T.; Pantet, O.; Hugli, O.; Carron, P.-N.; Meuwly, J.-Y.; Boillat-Blanco, N.

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 31st and May 8th, 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 (COVIDpos vs COVIDneg). 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 COVIDpos and 77% (n=103/134) were COVIDneg; 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 COVIDpos compared to COVIDneg (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 COVIDpos 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.