COVID-19 in Children: Correlation Between Epidemiologic, Clinical Characteristics, and RT-qPCR Cycle Threshold Values

Abstract

Background: Initially, the impact of SARS-CoV-2 infection on children was unknown. Standard COVID-19 diagnosis is confirmed using real-time qPCR. Cycle threshold (Ct) values of RT-qPCR are inversely proportional to viral load and the test indirectly quantifies viral RNA copy numbers. The objective of this study was to determine the correlation between epidemiology, clinical characteristics, severity of confirmed COVID-19 cases, and Ct values. Methods: An observational, analytical, cross-sectional study. All children with COVID-19 under 18 years old admitted to the Ricardo Gutiérrez Children’s Hospital between March 1, 2020, and February 28, 2021, were included. SARS-CoV-2 infection was confirmed using RT-qPCR. Results: Median age of patients was 7 years. Ct values were estimated in 419 cases, median Ct value was 23.5 [interquartile range (IQR): 18.9–30.9]. Levels were significantly lower in symptomatic than asymptomatic patients (Ct: 22.1; IQR: 18.4–22.1), in children <2 years of age (Ct: 20.6; IQR: 17.3–27.3) and when sample collection was 2 years, Ct values were significantly lower in symptomatic (Ct: 22.6; IQR: 18.7–29.3) than asymptomatic (Ct: 31.2; IQR: 24.5–33.3) patients. Conclusions: Children younger than 2 years with COVID-19 have lower values of Ct—as a proxy for higher viral load—than older children. Symptomatic children over 2 years of age had lower Ct values compared with asymptomatic children.