Abstract
BACKGROUND: Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigens in blood has high sensitivity in adults with acute coronavirus disease 2019 (COVID-19), but sensitivity in pediatric patients is unclear. Recent data suggest that persistent SARS-CoV-2 spike antigenemia may contribute to multisystem inflammatory syndrome in children (MIS-C). We quantified SARS-CoV-2 nucleocapsid (N) and spike (S) antigens in blood of pediatric patients with either acute COVID-19 or MIS-C using ultrasensitive immunoassays (Meso Scale Discovery). METHODS: Plasma was collected from inpatients (<21 years) enrolled across 15 hospitals in 15 us states. acute covid-19 patients (n =" 36)" had a range of disease severity and positive nasopharyngeal sars-cov-2 rt-pcr within 24 hours of blood collection. patients with mis-c (n =" 53)" met cdc criteria and tested positive for sars-cov-2 (rt-pcr or serology). controls were patients pre-covid-19 (n =" 67)" or within 24 hours of negative rt-pcr (n =" 43)." results: specificities of n and s assays were 95-97% and 100%, respectively. in acute covid-19 patients, n s plasma assays had 89% 64% sensitivity; sensitivities in patients with concurrent nasopharyngeal swab cycle threshold (ct) ≤35 were 93% 63%. antigen concentrations ranged from 1.28-3844 pg ml (n) and 1.65-1071 pg ml (s) and correlated with disease severity. in mis-c, antigens were detected in 3 53 (5.7%) samples (3 n-positive: 1.7, 1.9, 121.1 pg ml; 1 s-positive: 2.3 pg ml); the patient with highest n had positive nasopharyngeal rt-pcr (ct 22.3) concurrent with blood draw. conclusions: ultrasensitive blood sars-cov-2 antigen measurement has high diagnostic yield in children with acute covid-19. antigens were undetectable in most mis-c patients, suggesting that persistent antigenemia is not a common contributor to mis-c pathogenesis. diseases society of america. all rights reserved. for permissions, e-mail: journals.permissions@oup.com.>21>