Proportion of asymptomatic coronavirus disease 2019: A systematic review and meta‐analysis

Abstract

We aim to systematically review the characteristics of asymptomatic infection in the coronavirus disease 2019 (COVID‐19). PubMed and EMBASE were electronically searched to identify original studies containing the rate of asymptomatic infection in COVID‐19 patients before 20 May 2020. Then mate‐analysis was conducted using R version 3.6.2. A total of 50 155 patients from 41 studies with confirmed COVID‐19 were included. The pooled percentage of asymptomatic infection is 15.6% (95% CI, 10.1%‐23.0%). Ten included studies contain the number of presymptomatic patients, who were asymptomatic at screening point and developed symptoms during follow‐up. The pooled percentage of presymptomatic infection among 180 initially asymptomatic patients is 48.9% (95% CI, 31.6%‐66.2%). The pooled proportion of asymptomatic infection among 1152 COVID‐19 children from 11 studies is 27.7% (95% CI, 16.4%‐42.7%), which is much higher than patients from all aged groups. Abnormal CT features are common in asymptomatic COVID‐19 infection. For 36 patients from 4 studies that CT results were available, 15 (41.7%) patients had bilateral involvement and 14 (38.9%) had unilateral involvement in CT results. Reduced white blood cell count, increased lactate dehydrogenase, and increased C‐reactive protein were also recorded. About 15.6% of confirmed COVID‐19 patients are asymptomatic. Nearly half of the patients with no symptoms at detection time will develop symptoms later. Children are likely to have a higher proportion of asymptomatic infection than adults. Asymptomatic COVID‐19 patients could have abnormal laboratory and radiational manifestations, which can be used as screening strategies to identify asymptomatic infection.