Background

The time that RT-PCR remains positive in children with SARS-CoV-2 remains unclear.

The objectives of this study were:

- To determine the time between diagnosis and reverse transcription polymerase chain reaction (RT-PCR) negativization in children with COVID-19.

- To establish the relationship between cycle threshold (CT) at diagnosis (CTd) and time to negativization (TN) of PCR.

Methods

The Epidemiological Study of Coronavirus in Children (EPICO-AEP) is a multicentre cohort study conducted in Spain to assess the characteristics of children with COVID-19 from the beginning of the epidemic in Spain. This is a substudy focused on RT-PCR time to negativization.

After a confirmed diagnosis with RT-PCR, follow-up was performed at week 2, 3 and 4. Nasopharyngeal swab sampling for molecular detection of SARS-CoV-2 by RT-PCR was performed weekly until negativization or until 4 weeks after diagnosis. Data were analysed using Microsoft Excel® and GraphPrism®.

Results

Data from 294 patients were analysed. The median (IQR) TN was 18 days (8-29). Two weeks after diagnosis, 45.4% of patients remained RT-PCR positive; 21.6% did at week three and 9.4% at week four.

CTd value was available for 33 patients. Median CTd was 24 (IQR, 18-36). One-third (34.1%) had CTd≥35. When CTd≥35, TN was 9.5 days (8-20), while in CTd<35, TN was 17 days (8.5-24). Difference between CTd<35 and CTd≥35 subgroups was statiscally significant (U-Mann-Whitney p<0.05). However, CTd and TN did not correlate well (r Spearman: r: -0.34, p=0,053).

Conclusions

RT-PCR remains positive in children for a median of 18 days and remains positive 4 weeks later in 10% of children. This should be considered when testing children with symptoms consistent with COVID-19 and other diseases. Time to negativization did not correlate well with CT at diagnosis