Risk factors for re-detectable positivity in recovered COVID-19 children

OBJECTIVE To identify the risk factors for redetectable positivity (RP), and to provide a basis for prevention and control of coronavirus disease-2019 (COVID-19) in children. METHODS A retrospective study was performed on all pediatric patients diagnosed with COVID-19. RP was defined as the positive result of real-time reverse transcriptase polymerase chain reaction (RT-PCR) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after symptom resolution and discharge. Children were defined as being less than 18 years old. RESULTS Fourteen out of 38 (36.8%) pediatric patients exhibited RP. Compared with the non-RP group (n = 24), the RP group (n = 14) had more family cluster infections, relatively higher white blood cell (WBC) count and longer plasma prothrombin time (PT), while age and gender were insignificant. T lymphocyte subclassification was observed at five-time points: the first test after admission, 2 weeks, and 1, 2, and 3 months after discharge. The RP group had a higher percentage and count of CD8+ T lymphocytes and lower CD4+/CD8+ ratio at 2 weeks, while a lower percentage and count of CD4+ T lymphocytes and lower CD4+/CD8+ ratio at 2 months. The positive rate of nasopharyngeal swabs by RT-PCR was higher during the onset, while that of anal swabs was higher during the recovery of COVID-19. CONCLUSIONS Family cluster infection, higher WBC count, and longer PT are the early risk factors for RP in recovered COVID-19 children. The dynamic changes in number and ratio of CD4+ and CD8+ T lymphocytes may be involved in prolonged SARS-CoV-2 clearance. Nasopharyngeal swabs sampling during the onset and anal swabs sampling during the recovery may improve the positivity rate of RT-PCR.