The Relative Impact of Distinct Lung Ultrasound Aeration Score Patterns on Clinical Outcomes in COVID-19 Patients

Background: Within the lung ultrasound (LUS) score, A-lines, discrete B-lines, coalescent B-lines, and lobar consolidation represent scores of 0, 1, 2, and 3, respectively. However, the arbitrary ordinal values of 0 to 3 are not necessarily proportional to their clinical relevance. The objective of this study is to compare the relative strength of association between distinct LUS patterns on relevant clinical outcomes. Methods: This is a post hoc analysis of four prospective observational studies in COVID-19 subjects in the emergency department (ED) or in the ICU. Subjects were included if at least 3 zones per hemithorax were examined during ultrasound examination. Each LUS pattern was calibrated for relevant clinical outcomes based on the β coefficients derived from logistic and linear regression analyses, resulting in a rescaled LUS score. All scores were indexed using A-lines as a zero reference and discrete B-lines scaled to 1. Clinical outcomes were computed tomography severity score (CTSS), P/F ratio, ventilator-free days in the first 90 days (VFD-90), and 90-day mortality. Results: A total of 418 subjects were included, of which 114 were in the ED and 304 in the ICU. Increase in LUS score was associated with decreased VFD-90 and P/F ratio and increased CTSS and 90-day mortality. The rescaled LUS scores for P/F ratio and CTSS were smaller in magnitude than the original LUS scores (1, 1.24, 1.24 and 1, 1.48, 1.87, respectively), while rescaling for VFD-90 was larger in magnitude (1, 1.38, 2.83). The rescaled LUS score outperformed the original LUS score for every clinical outcome. Conclusions: The relative impact of LUS patterns differed depending on the clinical outcome of interest. The original arbitrary ordinal scores of 0 to 3 may not scale properly with any outcome. The LUS score may benefit from rescaling to reflect clinically meaningful outcomes more accurately.