Systematic lung ultrasound in Omicron-type vs. wild-type COVID-19

Abstract

Aims: Preliminary data suggested that patients with Omicron-type-Coronavirus-disease-2019 (COVID-19) have less severe lung disease compared with the wild-type-variant. We aimed to compare lung ultrasound (LUS) parameters in Omicron vs. wild-type COVID-19 and evaluate their prognostic implications.

Methods and results: One hundred and sixty-two consecutive patients with Omicron-type-COVID-19 underwent LUS within 48 h of admission and were compared with propensity-matched wild-type patients (148 pairs). In the Omicron patients median, first and third quartiles of the LUS-score was 5 [2-12], and only 9% had normal LUS. The majority had either mild (≤5; 37%) or moderate (6-15; 39%), and 15% (≥15) had severe LUS-score. Thirty-six percent of patients had patchy pleural thickening (PPT). Factors associated with LUS-score in the Omicron patients included ischaemic-heart-disease, heart failure, renal-dysfunction, and C-reactive protein. Elevated left-filling pressure or right-sided pressures were associated with the LUS-score. Lung ultrasound-score was associated with mortality [odds ratio (OR): 1.09, 95% confidence interval (CI): 1.01-1.18; P = 0.03] and with the combined endpoint of mortality and respiratory failure (OR: 1.14, 95% CI: 1.07-1.22; P < 0.0001). Patients with the wild-type variant had worse LUS characteristics than the matched Omicron-type patients (PPT: 90 vs. 34%; P < 0.0001 and LUS-score: 8 [5, 12] vs. 5 [2, 10], P = 0.004), irrespective of disease severity. When matched only to the 31 non-vaccinated Omicron patients, these differences were attenuated.

Conclusion: Lung ultrasound-score is abnormal in the majority of hospitalized Omicron-type patients. Patchy pleural thickening is less common than in matched wild-type patients, but the difference is diminished in the non-vaccinated Omicron patients. Nevertheless, even in this milder form of the disease, the LUS-score is associated with poor in-hospital outcomes.

Keywords: COVID-19; clinical outcomes; lung ultrasound; risk stratification.

Graphical abstract

Figure 1

Lung ultrasound points and examples of different patterns of lung ultrasound findings. (A) Probe positions in the anterior and antero-lateral positions (left and middle), and in the postero-lateral positions (right). (B) The different patterns of US findings and scoring (a) A-lines, normal reverberation artifacts of the pleural line that correspond to normal aeration of the lung. Lung ultrasound score (LUS) equals zero. (b) Separated two fine B-lines that represent reverberation artefact through mildly oedematous interlobular septa or alveoli that correspond to moderate aeration lost. LUS score equals one. (c) Multiple coalescent B-lines that correspond to severe lung aeration loss. LUS score equals two. (d) Lung consolidation (liver is on the left side of the picture, the consolidated lung on the right, and between them the dense line of the diaphragm) that correspond to complete aeration loss. LUS score equals three (e) Patchy pleural thickening. Compare to the fine plural line in picture a. (f) Pleural effusion with lower lobe passive lung atelectasis within.

Figure 2

Distribution of LUS grades in hospitalized patients with COVID-19 Omicron type.

Figure 3

LUS, chest X-ray, and hemodynamic parameters during acute wild-type vs. Omicron-type COVID-19 infection. For each parameter, the left and right columns respresent the Omicron-type and the wild-type variants, respectively. LUS: Lung ultrasound.