Lung ultrasound Score in COVID-19: cut-off points for severity degrees. A systematic review and validating cohort

Abstract

Aim: The purpose of this study is to establish different cut-off points based on the Lung Ultrasound Score (LUS) to identify COVID-19 patients as mild, moderate or severe cases. Material and methods: Systematic review of articles consistent with our cohort design, among PubMed, Embase, Scopus, Coronavirus Research Database and Cochrane Database of Systematic Reviews databases; from 31st December 2019 to 31st December 2021. Validated by single-centre prospective cohort of adult patients with confirmed SARS-CoV-2 infection, included within first 24 hours of admission. Studied variables were "poor outcome" and 28-days mortality. Results: From 510 articles, 11 articles were included, with a pooled population of 1308 patients; while 127 patients were admitted in our cohort. Only LUS > 15 for the prognostic endpoint "critical disease" could be validated. Both LUS > 15 and LUS > 17 proposed cut-off points showed statistically significant results for poor outcome in our cohort. It was established the reverse association between LUS and poor outcome (odds ratio [OR] = 0.304) and LUS and 28-days mortality (OR = 0.141). LUS < 7 showed high sensitivity (0.94), as LUS > 20 revealed high specificity (0.86). Conclusions: Lung ultrasound is a good predictor of poor outcome and 28-days mortality in COVID-19. LUS ≤ 7 cut-off point is associated with mild pneumonia, LUS 8-20 with moderate pneumonia (8-15 mild-moderate and 16-20 moderate-severe pneumonia) and ≥ 20 with severe pneumonia. If a single cut-off point were used, LUS > 15 is the cut-off point which better discriminate mild from severe disease.