Objectives: Investigate the feasibility of saliva sampling as a noninvasive and safer tool to detect SARS-CoV-2 and to compare its reproducibility and sensitivity with nasopharyngeal swab samples (NPS). The use of sample pools was also investigated .
Methods: 2107 paired samples were collected from asymptomatic health care and office workers in Mexico City . Sixty of these samples were also analyzed in two other independent laboratories for concordance analysis . Sample processing and analysis of virus genetic material were performed according to standard protocols described elsewhere . Pooling analysis was performed by analyzing the saliva pool and the individual pool components .
Results: The concordance between NPS and saliva results was 95.2% (Kappa : 0.727, p = 0.0001) and 97.9% without considering inconclusive results (Kappa : 0.852, p = 0.0001). Saliva had a lower number of inconclusive results than NPS (0.9% vs 1.9 %). Furthermore, saliva shows a significantly higher concentration of both total RNA and viral copies than NPS . Comparison of our results with those of the other two laboratories shows 100% and 97% concordance . Saliva samples are stable without the use of any preservative, a positive SARS-CoV-2 sample can be detected 5 , 10, and 15 days after collection when the sample is stored at 4 °C .
Conclusions: Our results indicate that saliva is as effective as NPS for the identification of SARS-CoV-2-infected asymptomatic patients, sample pooling facilitates the analysis of a larger number of samples with the benefit of cost reduction.