Chest CT Findings in Hospitalized Patients with SARS-CoV-2: Delta versus Omicron Variants.

ABSTRACT

Background CT manifestations of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may differ among variants. Purpose To compare the chest CT findings of SARS-CoV-2 between the Delta and Omicron variants. Materials and Methods This retrospective study collected consecutive baseline chest CT images of hospitalized patients with SARS-CoV-2 from a secondary referral hospital when the Delta and Omicron variants predominated. Two radiologists categorized CT images based on the Radiological Society of North America classification system for coronavirus disease 2019 (COVID-19) and visually graded pneumonia extent. Pneumonia, pleural effusion, and intrapulmonary vessels were segmented and quantified on CT images using a priori developed neural networks, followed by reader confirmation. Multivariable logistic and linear regression analyses were performed to examine the associations between the variants and CT category, distribution, severity, and peripheral vascularity. Results In total, 88 patients with the Delta (mean age, 67 years±15; 46 men) and 88 patients with the Omicron (mean age, 62 years±19; 51 men) variants were included. Omicron was associated with a less frequent typical peripheral, bilateral ground-glass opacity (32% [28/88] versus 57% [50/88]; P=.001), more frequent peri-bronchovascular predilection (38% [25/66] versus 7% [5/71]; P<.001), lower visual pneumonia extent (5.4±6.0 versus 7.7±6.6; P=.02), similar pneumonia volume (5%±10 versus 7%±11; P=.14), and a higher proportion of vessels with a cross-sectional area smaller than 5 mm2 relative to the total pulmonary blood volume (BV5%; 48%±11 versus 44%±8; P=.004). In adjusted analyses, Omicron was associated with a non-typical appearance (odds ratio, 0.34; P=.006), peri-bronchovascular predilection (odds ratio, 9.2; P<.001), and higher BV5% (ß value, 3.8; P=.01) but similar visual pneumonia extent (P=.17) and pneumonia volume (P=.67) relative to Delta variant. Conclusions On chest CT, the Omicron SARS-COV-2 variant showed nontypical, peri-bronchovascular pneumonia and less pulmonary vascular involvement than the Delta variant in hospitalized patients with comparable CT disease severity.