Population wide testing pooling strategy for SARS-CoV-2 detection using saliva

PLoS One. 2022 Jan 28;17(1):e0263033. doi: 10.1371/journal.pone.0263033. eCollection 2022.

Abstract

SARS-CoV-2 pandemic has forced frequent testing of populations. It is necessary to identify the most cost-effective strategies for the detection of COVID-19 outbreaks. Nasopharyngeal samples have been used for SARS-CoV-2 detection but require a healthcare professional to collect the sample and cause discomfort and pain to the individual. Saliva has been suggested as an appropriate fluid for the diagnosis of COVID-19. We have investigated the possibility of using pools of saliva samples to detect SARS-CoV-2 in symptomatic and asymptomatic patients. Two hundred and seventy-nine saliva samples were analyzed through RT-PCR of Envelope, Nucleocapsid and Open Reading Frame 1ab genes. Reproducibility assays showed an almost perfect agreement as well as high sensitivity (96.6%), specificity (96.8%), positive predicted value (96.6%), and negative predicted value (96.8%). The average Cycle Threshold of the genes detected was 29.7. No significant differences (p > 0.05) were detected when comparing the cycle threshold average of two consecutive reactions on the same positive saliva samples. Saliva samples have a higher median viral load (32.6) than in nasopharyngeal samples (28.9), although no significant differences were detected (p > 0.05). Saliva-pool samples allowed effective SARS-CoV-2 screening, with a higher sensibility (96.9%) on 10-sample pools than in 20-sample pools (87.5%). Regardless of pools size specificity was high (99.9%) and an almost perfect agreement was observed. Our strategy was successfully applied in population wide testing of more than 2000 individuals, showing that it is possible to use pooled saliva as diagnostic fluid for SARS-CoV-2 infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • COVID-19 / diagnosis
  • COVID-19 Testing / methods*
  • Humans
  • Reproducibility of Results
  • SARS-CoV-2 / isolation & purification*
  • Saliva / virology*
  • Sensitivity and Specificity
  • Specimen Handling / methods*

Grants and funding

This research was supported by grants from the Fundação para a Ciência e Tecnologia (UIDB/50017/2020+UIDP/50017/2020; PI: CESAM and UIDB/04279/2020 + UIDP/04279/2020; PI: CIIS and 226_596870204; PI: NR and CEECINST/00137/2018 and CEECINST/00137/2018). www.fct.pt/ The Funding entities had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.