Saliva as a reliable sample for COVID-19 diagnosis in paediatric patients

Diagnostic performance, stability, and acceptability of self-collected saliva without additives for SARS-CoV-2 molecular diagnosis

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the coronavirus disease 2019 (COVID-19), leading to a global pandemic. The molecular diagnosis of this virus is mostly performed by collecting upper respiratory samples, which has many disadvantages, including patient discomfort and the need for trained healthcare professionals. Although saliva has emerged as a more comfortable sample, the use of additives to preserve viral RNA is expensive and, in some cases, difficult for self-collection.

METHOD

This study evaluated the diagnostic performance by RT-PCR and stability of self-collected saliva using wide-mouth specimen collection cups without stabilization and/or inactivation buffers for SARS-CoV-2 detection, compared to nasopharyngeal samples and saliva collected with additives. Additionally, the study assessed the acceptability of this sample collection method among participants and healthcare personnel.

RESULTS

The study included 1281 volunteers with a 24.6% positive infection rate. Saliva demonstrated comparable diagnostic performance to nasopharyngeal samples, with a sensitivity of 87.6% and specificity of 99.6%, for a total percent agreement of 96.4%. The study also showed that viral RNA in saliva remained stable for at least 72 h at different temperatures. Notably, saliva samples without additives exhibited a lower RdRp Ct compared to samples with additives, suggesting that the absence of stabilization and/or inactivation buffers does not significantly affect its performance. The study highlighted the acceptability of saliva among patients and healthcare personnel due to its noninvasive nature and ease of collection.

CONCLUSIONS

This research supports the implementation of self-collected saliva as a comfortable and user-friendly alternative sample for SARS-CoV-2 diagnosis.

Saliva for molecular detection of SARS‐CoV ‐2 in preschool and school‐age children

SARS‐CoV‐2 diagnosis is a cornerstone for the management of coronavirus disease 2019 (COVID‐19). Numerous studies have assessed saliva performance over nasopharyngeal sampling (NPS), but data in young children are still rare. We explored saliva performance for SARS‐CoV‐2 detection by RT‐PCR according to the time interval from initial symptoms or patient serological status. We collected 509 NPS and saliva paired samples at initial diagnosis from 166 children under 12 years of age (including 57 children under 6), 106 between 12 and 17, and 237 adults. In children under 12, overall detection rate for SARS‐CoV‐2 was comparable in saliva and NPS, with an overall agreement of 89.8%. Saliva sensitivity was significantly lower than that of NPS (77.1% compared to 95.8%) in pre‐school and school‐age children but regained 96% when considering seronegative children only. This pattern was also observed to a lesser degree in adolescents but not in adults. Sensitivity of saliva was independent of symptoms, in contrary to NPS, whose sensitivity decreased significantly in asymptomatic subjects. Performance of saliva is excellent in children under 12 at early stages of infection. This reinforces saliva as a collection method for early and unbiased SARS‐CoV‐2 detection and a less invasive alternative for young children.