Prognostic implications and utility of LUS scoring
Y Lichter et al found the presence of pleural effusion, pleural thickening and a high total LUS score at baseline examination were significantly associated with increased mortality. The unadjusted hazard ratio of death for patients with LUS score >18 was 2.65 [1.14–6.3], p = 0.02, suggesting a 2.6-fold increase in mortality in those patients[86]. Extent of lung involvement on LUS was predictive of the need for intensive care unit admission as noted by Bonadia N et al, patients admitted to ICU had a median 93% of areas involved versus 20% of areas involved in patients who did not require ICU admission[92]. In a study by Zhao L et al., a LUS score cutoff point of 32 was found to predict refractory disease (defined as respiratory failure with a PaO2/FiO2 of ≤100 mm Hg or patients who were treated with ECMO) with a specificity of 89.3% and a sensitivity of 57.1%[93] Description of LUS scores in individual studies is provided in supplementary Table 2 . Castelao J et al used a self-designed scoring system to evaluate severity of lung involvement. The total lung score showed a strong correlation (r = −0.765) with the oxygen pressure–to–fraction of inspired oxygen ratio, and the anterior region lung score was significant (OR, 2.159; 95% confidence interval, 1.309–3.561) for the risk of requiring noninvasive respiratory support (NIRS)[84]. LUS score correlated with IL-6 concentrations (r = 0.52, p = 0.001) and arterial pCO2 (r = 0.30, p = 0.033) and was inversely correlated with oxygenation (r = − 0.34, p = 0.001) in mechanically ventilated patients with COVID-19[94].