A systematic review of chest imaging findings in COVID-19

Abstract

Chest computed tomography (CT) is frequently used in diagnosing coronavirus disease 2019 (COVID-19) for detecting abnormal changes in the lungs and monitoring disease progression during the treatment process. Furthermore, CT imaging appearances are correlated with patients presenting with different clinical scenarios, such as early versus advanced stages, asymptomatic versus symptomatic patients, and severe versus nonsevere situations. However, its role as a screening and diagnostic tool in COVID-19 remains to be clarified. This article provides a systematic review and meta-analysis of the current literature on chest CT imaging findings with the aim of highlighting the contribution and judicious use of CT in the diagnosis of COVID-19. A search of PubMed/Medline, Web of Science, ScienceDirect, Google Scholar and Scopus was performed to identify studies reporting chest imaging findings in COVID-19. Chest imaging abnormalities associated with COVID-19 were extracted from the eligible studies and diagnostic value of CT in detecting these abnormal changes was compared between studies consisting of both COVID-19 and non-COVID-19 patients. A random-effects model was used to perform meta-analysis for calculation of pooled mean values and 95% confidence intervals (95% CI) of abnormal imaging findings. Fifty-five studies met the selection criteria and were included in the analysis. Pulmonary lesions more often involved bilateral lungs (78%, 95% CI: 45-100%) and were more likely to have a peripheral (65.35%, 95% CI: 25.93-100%) and peripheral plus central distribution (31.12%, 95% CI: 1.96-74.07%), but less likely to have a central distribution (3.57%, 95% CI: 0.99-9.80%). Ground glass opacities (GGO) (58.05%, 95% CI: 16.67-100%), consolidation (44.18%, 95% CI: 1.61-71.46%) and GGO plus consolidation (52.99%, 95% CI: 19.05-76.79%) were the most common findings reported in 94.5% (52/55) of the studies, followed by air bronchogram (42.50%, 95% CI: 7.78-80.39%), linear opacities (41.29%, 95% CI: 7.44-65.06%), crazy-paving pattern (23.57%, 95% CI: 3.13-91.67%) and interlobular septal thickening (22.91%, 95% CI: 0.90-80.49%). CT has low specificity in differentiating pneumonia-related lung changes due to significant overlap between COVID-19 and non-COVID-19 patients with no significant differences in most of the imaging findings between these two groups (P>0.05). Furthermore, normal CT (13.31%, 95% CI: 0.74-38.36%) was reported in 26 (47.3%) studies. Despite widespread use of CT in the diagnosis of COVID-19 patients based on the current literature, CT findings are not pathognomonic as it lacks specificity in differentiating imaging appearances caused by different types of pneumonia. Further, there is a relatively high percentage of normal CT scans. Use of CT as a first-line diagnostic or screening tool in COVID-19 is not recommended.

Keywords: COVID-19; Coronavirus infections; computed tomography (CT); diagnosis; imaging; sensitivity; specificity.

Figure 1

Flow chart showing the selection process of identifying studies that met the inclusion criteria.

Figure 2

Bilateral lung involvement in a 50-year-old male diagnosed with COVID-19. An axial CT image shows multiple patchy areas of pure ground glass opacities.

Figure 3

Ground glass opacity (GGO) in a 68-year-old female with confirmed COVID-19. Axial CT images shows multiple round morphology of GGOs in the bilateral upper lobes. Lesions are located in peripheral lung fields.

Figure 4

Consolidation in a 48-year-old man with COVID-19 pneumonia. (A,B) CT images show bilateral multiple lobular and subsegmental areas of consolidation with a clear margin.

Figure 5

Crazy-paving pattern in two patients with COVID-19. (A) A 72-year-old woman with lesions more severe on the left lung compared with the right lung. (B) A 51-year-old man showing increased opacities of consolidation in both the lungs with presence of air bronchogram.

Figure 6

Air bronchogram in two patients with COVID-19 pneumonia. (A) In a 76-year-old man, air bronchogram is seen in multiple GGO lesions. (B) In a 73-year-old male, air bronchogram is clearly seen in extensive consolidation areas in both the lungs. GGO, ground glass opacity.

Figure 7

Linear opacities in a 48-year-old male with COVID-19. (A,B) CT images show multiple linear shadows seen in the bilateral lungs. (C) HRCT reveals linear opacities more clearly than standard CT. The opacities are predominantly distributed peripherally. HRCT, high resolution computed tomography.

Figure 8

Local and bilateral patchy shadowing in a 63-year-old female with COVID-19. (A) CT image at the initial examination shows small patchy shadows in the peripheral regions of both the lungs. (B) CT taken 5 days later shows apparent progression of disease with increased density areas in both the lungs.

Figure 9

Interlobular septal thickening in a 63-year-old man with COVID-19 pneumonia. (A,B,C) Multiple consolidation areas with interlobular septal thickening (arrows) are seen on both the lungs. The disease has a prominent peripheral distribution.

Figure 10

Fibrous stripes in two patients with COVID-19. (A) In a 48-year-old woman, fibrous streak lesion (arrow) is noted in the right lower lung. (B,C) In a 56-year-old woman, multiple fibrous stripes are seen in the peripheral regions of both the lower lungs.

Figure 11

A 52-year-old man with COVID-19. High-resolution CT image shows ground glass opacities with vascular enhancement (arrows).

Figure 12

Bronchiectasis in two patients with COVID-19 pneumonia. (A) In a 50-year-old man, multiple patchy shadows are observed in the bilateral peripheral lung fields with dilated bronchia (arrows). (B) In a 73-year-old man, multiple consolidation areas are seen in both the lungs and dilated bronchi within the density areas of the right lung (arrows).

Figure 13

Pleural effusion in a 78-year-old male with COVID-19 pneumonia. Consolidation is seen in the bilateral lower lung fields with air bronchogram. Pleural effusion is present on both sides.

Figure 14

Pulmonary nodule in a 23-year-old female with confirmed COVID-19. (A) Initial CT image on January 26, 2020 shows a nodule in the left lower lung. (B,C) The lesion progressed with a patchy shadow on CT images taken on January 30 and February 5, 2020. (D) CT scan on March 2, 2020 shows resolution of the nodule.