Table 1. Summary table of the characteristics and key findings of significant studies mentioned in this narrative review.

Primary study	Country	Type of study	Population size	Outcomes	Ref.
CT scan studies
Zhu et al.	China	Meta-analysis	4121	The results of the meta-analysis showed that most patients presented bilateral lung involvement (73.8%) or multilobar involvement (67.3%). The most common changes in lesion density were GGOs (68.1%). In addition, the paper recommends using CT for screening patients with a negative RT-PCR result who have epidemiological and clinical features of COVID-19.	[10]
Xu et al.	China, Japan	Meta-analysis	3186	Sixteen studies were included in the meta-analysis. CT sensitivity was 92% (95% CI: 86–96%), and two studies reported specificity (25% [95% CI: 22–30%] and 33% [95% CI: 23–44%], respectively). There was substantial heterogeneity according to Cochran's Q test (p < 0.01) and Higgins I2 heterogeneity index (96% for sensitivity). Based on study site, the sensitivity of chest CT was great in Wuhan and the sensitivity values were very close to each other (97, 96 and 99%, respectively). In the regions other than Wuhan, the sensitivity varied from 61 to 98%.	[16]
Adams et al.	China, Italy, Japan	Meta-analysis	1431	Six studies were included in the meta-analysis. The sensitivity of chest CT ranged from 92.9 to 97.0%, and specificity ranged from 25.0 to 71.9%, with pooled estimates of 94.6% (95% CI: 91.9–96.4%) and 46.0% (95% CI: 31.9–60.7%), respectively. The included studies were statistically homogeneous in their estimates of sensitivity (p = 0.578) and statistically heterogeneous in their estimates of specificity (p < 0.001). Chest CT appears to have a relatively high sensitivity in symptomatic patients at high risk of COVID 19, however, specificity is poor.	[19]
Kanne et al.	China	Retrospective study	9720	The most common presentations were fever (98%), cough (76%) and myalgia or fatigue (44%). Dyspnea has been reported in 55% of patients. CT findings were 86% GGOs and 29% consolidation	[18]
Ai et al.	China	Retrospective study	1014	Fifty-nine percent had positive RT-PCR results, and 88% had positive chest CT scans. The sensitivity of chest CT in suggesting COVID-19 was 97% based on positive RT-PCR results. In patients with initial negative RT-PCR results, 75% had positive chest CT findings. In patients with negative RT-PCR results but positive chest CT scans (n = 308 patients), 48% (147/308) of patients were re-considered as highly likely cases, with 33% (103/308) as probable cases by a comprehensive evaluation.	[2]
Bai et al.	USA & China	Retrospective study	219	The most discriminating features for COVID-19 pneumonia included a peripheral distribution (80 vs 57%; p < 0.001), GGO (91 vs 68%; p < 0.001) and vascular thickening (58 vs 22%; p < 0.001). Three Chinese radiologists had sensitivities of 72, 72 and 94% and specificities of 94, 88 and 24%. Four US radiologists had sensitivities of 93, 83, 73 and 73% and specificities of 100, 93, 93 and 100%.	[21]
Zhao et al.	China	Retrospective study	101	A total of 70.2% of the patients were 21–50 years old. 78.2% had fever as the onset symptom. GGO 86.1% or mixed GGO and consolidation 64.4%, vascular enlargement in the lesion 71.3%. Lesions present on CT images were more likely to have a peripheral distribution 87.1%	[7]
Xie et al.	China	Retrospective study	167	The RT-PCR and CT were concordant for 2019-nCoV infection in 93%. Three percent of the patients initially had negative RT-PCR but positive chest CT with pattern consistent with viral pneumonia. Four percent had a negative chest CT with a positive RT-PCR.	[17]
Song et al.	China	Retrospective study	51	Chest CT showed pure GGOs in 77% of patients, GGOs with interstitial and/or interlobular septal thickening in 75% of patients, and GGOs with consolidation in 59% of patients. At chest CT, GGOs were bilateral in 88% of patients, involving the posterior lungs in 82% and the peripheral lungs in 85% of patients.	[12]
Fang et al.	China	Retrospective study	51	Seventy-one percent of the patients had initial positive RT-PCR for COVID-19.Twenty-four percent of the patients had COVID-19 confirmed by two RT-PCR nucleic acid tests (1–2 days), (72%) had typical CT manifestations such as GGO's and consolidation.	[14]
Chest x-ray studies
Wang et al.	Canada	Dataset	13870	COVID-Net is one of the first open source network designs for COVID-19 detection from CXR images at the time of initial release. The introduction of COVIDx, an open access benchmark dataset. The dataset has the largest number of publicly available COVID-19 positive cases to the best of the authors’ knowledge.	[22]
Wong et al.	Hong Kong, China	Retrospective study	64	In a cohort of patients with COVID-19 infection and imaging follow-up, baseline chest x-ray had a sensitivity of 69%, compared with 91% for initial RT-PCR. Chest x-ray abnormalities preceded positive RT-PCR in 6/64 (9%) patients. Common chest x-ray findings mirror those previously described for CT: bilateral, peripheral, consolidation and/or GGO.	[23]

Using PubMed and Google Scholar, studies that were included were based on the following search strategy; COVID-19, CT scan, CXRs, RT-PCR and imaging. We excluded studies that did not address the topic of interest.

COVID-19: Novel coronavirus disease 2019; CT: Computed tomography; CXR: Chest x-ray; GGO: Ground-glass opacity; RT-PCR: Reverse transcriptase PCR.