Dynamics of RT-PCR and Serologic Test Results in Children with SARS-CoV-2 Infection

Tagarro, A.; Sanz-Santaeufemia, F.J.; Grasa, C.; Cobos, E.; Yebra, J.; Alonso-Cadenas, J.A.; Baquero-Artigao, F.; Mesa, Guzmán JM.; Perez, Seoane B.; Calvo, C.; Herreros, M.L.; Epalza, C.; Melendo, S.; Dominguez-Rodriguez, S.; Vidal, P.; Pacheco, M.; Ballesteros, A.; Bernardino, M.; Villanueva-Medina, S.; Rodríguez, Molino P.; Miragaya, Castro S.; Rivière, J.; Garcés, R.; Santiago, B.; Fumadó, V.; Urretavizcaya-Martínez, M.; García-García, M.L.; Penín, M.; Cava, F.; Sáez, E.; Iglesias-Bouzas, M.I.; Herrero, B.; Reinoso, T.; Moraleda, C.

OBJECTIVES: To determine the time to RT-PCR negativity after the first positive RT-PCR test, factors associated with longer time to RT-PCR negativity, proportion of children seroconverting after proven SARS-CoV-2 infection, and factors associated with the lack of seroconversion. STUDY DESIGN: EPICO-AEP is a multicenter study conducted in Spanish children to assess the characteristics of COVID-19. In a subset of patients, three serial RT-PCR tests on nasopharyngeal swab specimens were performed after the first RT-PCR test, and IgG serology for SARS-CoV-2 antibodies was performed in the acute and follow up (<14 and ≥14 days after diagnosis) phase. RESULTS: In total, 324 patients were included in the study. Median [IQR] time to RT-PCR negativity was 17 [8–29] days, and 35% of patients remained positive >4 weeks after the first RT-PCR test. The probability of RT-PCR negativity did not differ across groups defined by sex, disease severity, immunosuppressive drugs, or clinical phenotype. Globally, 24% of children failed to seroconvert after infection. Seroconversion was associated with hospitalization, persistence of RT-PCR positivity and days of fever. CONCLUSIONS: Time to RT-PCR negativity was long, regardless of severity of symptoms or other patients’ features. This should be considered when interpreting RT-PCR results in a child with symptoms, especially those with mild symptoms. Seroprevalence and post-immunization studies should consider that one in four infected children fail to seroconvert.