Chest CT Severity Score: An Imaging Tool for Assessing Severe COVID-19

Abstract

Purpose: To evaluate the value of chest CT severity score (CT-SS) in differentiating clinical forms of coronavirus disease 2019 (COVID-19).

Materials and methods: A total of 102 patients with COVID-19 confirmed by a positive result from real-time reverse transcription polymerase chain reaction on throat swabs who underwent chest CT (53 men and 49 women, 15-79 years old, 84 cases with mild and 18 cases with severe disease) were included in the study. The CT-SS was defined by summing up individual scores from 20 lung regions; scores of 0, 1, and 2 were respectively assigned for each region if parenchymal opacification involved 0%, less than 50%, or equal to or more than 50% of each region (theoretic range of CT-SS from 0 to 40). The clinical and laboratory data were collected, and patients were clinically subdivided according to disease severity according to the Chinese National Health Commission guidelines.

Results: The posterior segment of upper lobe (left, 68 of 102; right, 68 of 102), superior segment of lower lobe (left, 79 of 102; right, 79 of 102), lateral basal segment (left, 79 of 102; right, 70 of 102), and posterior basal segment of lower lobe (left, 81 of 102; right, 83 of 102) were the most frequently involved sites in COVID-19. Lung opacification mainly involved the lower lobes, in comparison with middle-upper lobes. No significant differences in distribution of the disease were seen between right and left lungs. The individual scores in each lung and the total CT-SS were higher in severe COVID-19 when compared with mild cases (P < .05). The optimal CT-SS threshold for identifying severe COVID-19 was 19.5 (area under curve = 0.892), with 83.3% sensitivity and 94% specificity.

Conclusion: The CT-SS could be used to evaluate the severity of pulmonary involvement quickly and objectively in patients with COVID-19.© RSNA, 2020.

Figure 1:

Number of patients involved in each lung segment.

Figure 2:

A-C, Noncontrast chest CT images in a 46-year-old woman with mild COVID-19 pneumonia. CT images show ground-glass opacities in the posterior segment of right upper lobe, superior segment of bilateral lungs, and posterior basal segment of right left lobe, and the CT-SS is 4. D-F, Noncontrast chest CT images in a 20-year-old man with mild COVID-19 pneumonia. CT images show ground-glass opacities and consolidation in multiple lung segments, and the CT-SS is 7.

Figure 3:

A-C, Noncontrast chest CT images in a 56-year-old man with severe COVID-19 pneumonia. CT images show multiple ground-glass opacities in multiple lung segments, and the CT-SS is 28. D-F, Noncontrast chest CT images in a 69-year-old man with severe COVID-19 pneumonia. CT images show multiple ground-glass opacities and septal thickening; the imaging manifestation is the so-called white lungs; the CT-SS is 35.

Figure 4:

ROC curve for CT-SS.