Comparison of Computed Tomography and Clinical Features Between Patients Infected with the SARS-CoV-2 Omicron Variant and the Original Strain

Abstract

Purpose: To investigate potential differences in clinical and computed tomography (CT) features between patients with the SARS-CoV-2 Omicron variant and the original strain.

Patients and methods: This retrospective study included 69 hospitalized patients infected with Omicron variant from November to December 2022, and 96 hospitalized patients infected with the original strain from February to March 2020 in Chongqing, China. The clinical features, CT manifestations, degrees of lung involvement in different stages on CT, and imaging changes after the reverse-transcription polymerase chain reaction (RT-PCR) results turned negative were compared between the two groups.

Results: For clinical features, patients with Omicron were predominantly old people and females, without manifestation of any clinical symptoms, who had low serum levels of C-reactive protein and procalcitonin. Shorter interval from symptoms onset to initial CT scan was observed in Omicron patients compared to patients with the original strain (all P < 0.05). For CT features, patients with Omicron were more likely to present with round-like opacities and tree-in-bud pattern (all P < 0.05), but less likely to exhibit a diffuse distribution, patchy and linear opacities, as well as vascular enlargement pattern (all P < 0.05). The Omicron group was more susceptible to exhibiting lower CT involvement scores in each stage (all P < 0.05) and imaging progression after the RT-PCR results turned negative (P < 0.001).

Conclusion: Patients infected with the Omicron variant exhibited less severe changes on chest CT compared to those infected with the original strain. Furthermore, imaging progression under low viral load conditions was more common in patients with Omicron than in those with the original strain.

Keywords: computed tomography; pneumonia; severe acute respiratory syndrome coronavirus-2.

Figure 1

Flow diagram for patient selection in this study.

Figure 2

A 52-year-old female patient infected with Omicron strain. (A and B) Axial computed tomography (CT) images show multiple round-like ground-glass opacities (GGOs) distributed peripherally in both lungs.

Figure 3

A 47-year-old female patient infected with the Omicron variant. (A and B) Axial computed tomography (CT) images exhibit a tree-in-bud pattern (red arrow) and patchy ground-glass opacities (GGOs) in the right upper lobe.

Figure 4

A 44-year-old male patient infected with the original strain. (A and B) Axial computed tomography (CT) images show patchy ground-glass opacities (GGOs) distributed peripherally of both lungs.

Figure 5

A 60-year-old male patient infected with the original strain. (A and B) Axial computed tomography (CT) images show linear opacities (blue arrow) and multiple subpleural ground-glass opacities (GGOs) in both lungs with a vascular enlargement pattern (red arrow).

Figure 6

An 80-year-old male patient infected with the Omicron variant. (A–C) Initial computed tomography (CT) images revealed a few patchy ground-glass opacities (GGOs) in both lungs. (D–F) Four days later, this patient’s RT-PCR results turned negative, but his respiratory tract symptoms were aggravated with a progressive increase in the levels of interleukin-6. Follow-up CT images showed imaging progress with increased GGOs in both lungs. (G–I) Eight days later, follow-up CT images showed that GGOs were further increased in both lungs, accompanied by a crazy-paving pattern and small pleural effusion.