Should computed tomography (CT) be used as a screening or follow-up tool for asymptomatic patients with SARS-CoV-2 infection?

The corona virus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome corona virus 2 (SARSCoV-2), was first reported in China in December 2019. As of 10 AM on March 28, 2020, there have been 571,678 confirmed patients and 26,494 deaths around the world, and the affected area is still expanding (1). The gold standard for the diagnosis of COVID-19 is the real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay of the pharyngeal swab specimen. However, due to its inadequate test kit in some areas, computed tomography (CT) examination has been used as a screening and followup tool in China (2,3). Symptomatic patients with negative initial RT-PCR detection might show lesions on CT (4). There are mainly four types of intrapulmonary lesions of COVID-19 including pure ground-glass opacity (GGO), GGO lesions with reticular and/or interlobular septal thickening, GGO with consolidation, GGO with reticular and/or interlobular septal thickening. Pulmonary lesions are frequently confined to the peripheral area of the lungs and involved bilateral lungs with the right lower lobe most affected (5,6). Mediastinal lymphadenopathy, pleural effusion, pulmonary emphysema and other signs are rare. However, CT examination has the disadvantage of radiation dose and COVID-19 can be self-limiting. Bernheim et al. (7) reported that CT was normal in 56% of patients within 0–2 days after symptoms appeared, indicating that CT was thereby unlikely a reliable standalone tool to rule out COVID-19 infection. Xu et al. (8) reported two asymptomatic children and adolescent RTPCR confirmed patients (50% of their family cluster cases) had no lesion both on initial and follow-up CT. Wáng (9) pointed out that in the general population, the proportion of patients with no or few symptoms would be larger, and the positive rate of CT would be lower, but such rate in asymptomatic patients is still unknown. Therefore, the application of CT in screening and the follow-up of asymptomatic COVID-19 patients is controversial.