Chest CT Imaging Signature of Coronavirus Disease 2019 Infection: In Pursuit of the Scientific Evidence

Abstract

Background: Chest CT may be used for the diagnosis of coronavirus disease 2019 (COVID-19), but clear scientific evidence is lacking. Therefore, we systematically reviewed and meta-analyzed the chest CT imaging signature of COVID-19.

Research question: What is the chest CT imaging signature of COVID-19 infection?

Study design and methods: A systematic literature search was performed for original studies on chest CT imaging findings in patients with COVID-19. Methodologic quality of studies was evaluated. Pooled prevalence of chest CT imaging findings were calculated with the use of a random effects model in case of between-study heterogeneity (predefined as I² ≥50); otherwise, a fixed effects model was used.

Results: Twenty-eight studies were included. The median number of patients with COVID-19 per study was 124 (range, 50-476), comprising a total of 3,466 patients. Median prevalence of symptomatic patients was 99% (range, >76.3%-100%). Twenty-seven of the studies (96%) had a retrospective design. Methodologic quality concerns were present with either risk of or actual referral bias (13 studies), patient spectrum bias (eight studies), disease progression bias (26 studies), observer variability bias (27 studies), and test review bias (14 studies). Pooled prevalence was 10.6% for normal chest CT imaging findings. Pooled prevalences were 90.0% for posterior predilection, 81.0% for ground-glass opacity, 75.8% for bilateral abnormalities, 73.1% for left lower lobe involvement, 72.9% for vascular thickening, and 72.2% for right lower lobe involvement. Pooled prevalences were 5.2% for pleural effusion, 5.1% for lymphadenopathy, 4.1% for airway secretions/tree-in-bud sign, 3.6% for central lesion distribution, 2.7% for pericardial effusion, and 0.7% for cavitation/cystic changes. Pooled prevalences of other CT imaging findings ranged between 10.5% and 63.2%.

Interpretation: Studies on chest CT imaging findings in COVID-19 suffer from methodologic quality concerns. More high-quality research is necessary to establish diagnostic CT criteria for COVID-19. Based on the available evidence that requires cautious interpretation, several chest CT imaging findings appear to be suggestive of COVID-19, but normal chest CT imaging findings do not exclude COVID-19, not even in symptomatic patients.

Keywords: COVID-19; CT; chest; meta-analysis; systematic review.

Figure 1

Flowchart of the study selection process. The asterisk indicates that, after duplicates were discarded, 3,060 articles remained. The number sign indicates that 72 studies were excluded because they included <50 patients, that 46 studies were excluded because they did not provide a detailed description of chest CT imaging findings, that 13 studies were excluded because of (potential) duplicate reporting of patient data, that four studies were excluded because of reporting the sum of findings of multiple chest CT scans performed in the same patients at different times, that one study was excluded because it evaluated the value of CT scans of other regions of the body than the chest, and that one study was excluded because it included patients without real time polymerase chain reaction-confirmed coronavirus disease 2019 infection (e-Appendix 1).

Figure 2

A 76-year-old man with real-time polymerase chain reaction-confirmed coronavirus disease 2019 had had a cough and fever for 2.5 weeks. Axial chest CT image shows bilateral, multifocal ground-glass opacities that were predominantly located peripherally (arrows).

Figure 3

A 57-year-old man with real-time polymerase chain reaction-confirmed coronavirus disease 2019 had had a cough, dyspnea, and fever for eight days. Axial chest CT image shows bilateral, multifocal ground-glass opacities/consolidations (arrows) with a posterior part/lower lobe predilection. Air bronchograms are also present (arrowheads).

Figure 4

A 62-year-old man with real-time polymerase chain reaction-confirmed coronavirus disease 2019 had experienced fatigue and fever for one week. For two days, a cough and dyspnea were also present. Axial chest CT image shows subpleural curvilinear opacity in the left lower lobe (arrows). In addition, there are multifocal areas of consolidation and ground-glass opacity in both lungs (arrowheads).

Figure 5

A 71-year-old woman with real-time polymerase chain reaction-confirmed coronavirus disease 2019 had had symptoms of progressive dyspnea, nausea, and diarrhea for one week. Axial chest CT image shows bilateral, multifocal ground-glass opacities that are distributed in a posterior part/lower lobe predilection. Vascular thickening is present in the right lower lobe (arrows).

Figure 6

A 69-year-old woman with real-time polymerase chain reaction-confirmed coronavirus disease 2019 had been sick for ten days with a cough, dyspnea, and fever that fluctuated. There had been no improvement after antibiotic therapy. Axial chest CT image shows extensive area of ground-glass opacity with predominant diffuse right lung involvement and the presence of air bronchograms (arrowheads).