Imaging Progression Under Low Respiratory Viral Load of SARS-CoV-2 Omicron Variant Infection: A Retrospective Study in China

Abstract

Purpose: To investigate the computed tomography (CT) findings of SARs-CoV-2 Omicron variant in relation to respiratory viral loads determined by cycle threshold values in reverse-transcription polymerase chain reaction (RT-PCR).

Materials and methods: From October 2022 to November 2022, 74 hospitalized patients with Omicron were included in this retrospective study. The radiological features, CT involvement scores in relation to the respiratory viral load, and factors associated with imaging progression (IP) after the RT-PCR results turned negative were analyzed.

Results: The most common CT patterns of Omicron were multiple round-like or patchy ground-glass opacity (GGO) or mixed GGO in the peripheral or diffuse areas. The grading of CT involvement scores exhibited an inverse pattern compared to viral loads from day 1 to day 8 and from day 13 to day 20 after diagnosis. Among the 65 patients with complete imaging data, 45 (69.23%) showed IP with clinical warning indicators of disease exacerbation negative in 34 and positive in 11. Patients with IP were older than those with non-IP (NIP); the erythrocyte sedimentation rates, procalcitonin levels, and D-dimer levels on admission of patients with IP were significantly higher than those of patients with NIP, whereas the immunoglobulin (Ig) G antibody level on admission and CT involvement score on initial CT of patients with IP were significantly lower than those of patients with NIP (all P < 0.05).

Conclusion: For patients with Omicron, the IP of lung abnormalities is common when the viral load decreases. Under these circumstances, paying attention to clinical warming indicators of disease progression may contribute to better patient management and the mitigation of severe pneumonia.

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

Figure 1

Flowchart of the patient inclusion process.

Figure 2

Typical chest computed tomography manifestations of a 67-year-old man infected with the Omicron variant. (a–d) Axial computed tomography images show round-like and patchy ground-glass opacity in the peripheral areas of both lungs accompanied by vascular enlargement patterns (red arrow).

Figure 3

Dynamics of the grades of computed tomography involvement scores and respiratory viral loads according to the time from the initial positive reverse-transcription polymerase chain reaction. From the 1st to the 8th day, the grade of the viral load decreases gradually, whereas the grade of the computed tomography involvement scores increases. From the 8th to 13th day, the grade of the computed tomography involvement scores and respiratory viral loads are maintained at similar levels. From the 13th to 20th day, the grade of the computed tomography involvement scores increases continuously, whereas that of the viral loads declines to a low level.

Figure 4

Sequential chest computed tomographic images of an 87-year-old woman infected with the Omicron variant. (a–c) Initial computed tomography images show a few peripheral ground-glass opacities (GGOs) and linear shadows in both lungs on the 2nd day after diagnosis. (d–f) Twelve days later when the reverse-transcription polymerase chain reaction results became negative, the follow-up computed tomography images revealed imaging progress with bilateral multi-patchy GGO displaying crazy-paving patterns, intralobular lines, vascular enlargement patterns, and pleural effusion. (g–i) After another seven days, follow-up computed tomography images demonstrated an obvious absorption of lung abnormalities after corticosteroids and immunoglobulin therapy.