Early CT Findings of Coronavirus Disease 2019 (COVID-19) in Asymptomatic Children: A Single-Center Experience

Coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus initially identified in Wuhan, China, in December 2019 (1). By March 11, 2020, the pathogen had been rapidly spread to 113 countries worldwide (2). COVID-19 has typical manifestations of acute pneumonia and severe complications such as acute respiratory distress syndrome, and its mortality rate was estimated to be approximately 2% (2, 3, 4). Since it is a highly infectious disease and transmission by asymptomatic patients has been proven (5), early detection and diagnosis are of significant importance in disease control and treatment. Radiological characteristics provide important evidence for the clinical diagnosis of COVID-19. According to previous studies (6, 7, 8, 9, 10, 11), bilateral and peripheral predominant ground-glass opacity (GGO) or mixed GGO and consolidation with signs such as crazy paving, air bronchogram, and interstitial thickening were common findings in adult patients diagnosed with COVID-19. However, information regarding pediatric clinical and radiological features of COVID-19 is insufficient (12, 13, 14, 15). This study aimed to describe a pediatric case series diagnosed with COVID-19 in detail to illustrate early computed tomography (CT) findings.

The study was approved by the Institutional Review Board of Zhongnan Hospital of Wuhan University (approval number 2020004). The requirement for written informed consent was waived.

A low percentage (0.4%, 6 of the 1574 patients) of pediatric patients aged less than 14 years was diagnosed with COVID-19 in our center, which was consistent with the results previously reported by Guan et al. (17) (0.9%). According to previous studies (12, 13, 14, 15, 17), most pediatric cases of COVID-19 were mild and showed symptoms similar to those of adult cases. The reported four patients were subclinical cases and had good prognoses after a disease course ranging from 7 to 15 days. Notably, for Patient 4 with one lesion on CT images and no new lesion arising during treatment, a significantly longer time interval was observed from confirmation to first negative RT-PCR (12 days) compared with the other three patients. This suggested that the duration of viral shedding might not be associated with disease severity evaluated with CT scan.

Regarding laboratory findings, lymphopenia or leucopenia was not observed, although they were common findings in most adult patients diagnosed with COVID-19 (3, 17). A remarkable increase in procalcitonin levels and a significant proportion of coinfection were observed among pediatric patients according to Xia et al.'s study (13), and this finding was not observed in the current four patients. One child had hepatic dysfunction upon admission and recovered quickly after treatment. After ruling out hepatitis, it was considered possible that the hepatic damage was caused by COVID-19, which had been previously reported in adult patients (18).

Considering that RT-PCR test was time consuming and showed high false-negative rate in China (19), radiological findings were considered important in infection detection and disease control. Although chest radiography is a regular examination, it was not recommended for COVID-19 due to its low sensitivity and nonspecific manifestation, which had been reported in several studies (10, 15). As most pediatric patients were mild or moderate cases of COVID-19, the rate of misdiagnosis by radiography might be higher for children than for adults, leading to delayed isolation and treatment for at least a proportion of pediatric patients with initial false-negative RT-PCR results. Compared to radiography, thin-section CT was more sensitive to subtle changes in early infection and was recommended by the guidelines for imaging diagnosis of COVID-19 in China (20).

In adult patients, bilateral lung involvement was frequently observed in most patients; peripherally located GGO or mixed GGO and consolidation in CT images were typical findings, with or without crazy paving, interstitial thickening, or air bronchogram signs (7, 9, 10, 11). These manifestations were similar but milder in pediatric patients. In the current study, unilateral involvement was observed in two of the four patients. Predilection of peripheral or subpleural distribution could be observed, and the lower lobes were more likely to be infected, which was observed in a previous study (12) and in adult patients (19). A majority of patients in this study showed small patches of GGO with ill-defined borders, and consolidation surrounded by the halo sign was not as common as had been reported previously (4). One possible explanation is that consolidation tends to develop in the progressive stage (7, 21). CT signs such as crazy paving, interstitial thickening, and air bronchogram were infrequently observed due to the relatively smaller lesions in children (diameter < 1 cm). Reticular pattern, parenchymal band, pleural changes, lymphadenopathy, and pleural effusion were not observed in the current study.

All four children reported familial cluster transmission, which was consistent with the reported transmission pattern among infants (22). Thus, adult family members with high risk factors of COVID-19 infection should pay special attention when in direct contact with children. Additionally, since some pediatric infections have an asymptomatic or mild manifestation, attention should be paid to potential transmission by such cases as asymptomatic carrier transmission has already been proven (5).

The current study had a small sample size, which is a limitation. Hence, further investigation with a large cohort is required to understand the full disease spectrum among children with COVID-19. Additionally, radiography findings from the four children were not available because CT was the recommended examination for both adult and pediatric COVID-19 patients according to the guidelines for imaging diagnosis of COVID-19 in China (20). However, considering that pediatric COVID-19 tends to be mild and different from adult cases, the recommendation of CT as a routine radiological examination for pediatric patients awaits further evidence to carefully weigh the benefits and risks of CT.

In summary, a pediatric case series of COVID-19 was described. Although similar to adult patients, pediatric patients tended to experience mild manifestations of COVID-19. Regarding CT features, small patches of GGO with subpleural distribution and unilateral lung involvement were common findings in pediatric patients in the early stage of the disease. Consolidation surrounded by the halo sign could also be observed. Margins of lesions were ill-defined. Lower lobes were predominantly infected. All exudative lesions were substantially resolved after treatment, and patients had good prognoses. Additionally, familial cluster was the main transmission pattern of these pediatric infections. Potential asymptomatic carrier transmission by pediatric patients should be further studied.