Does sampling saliva increase detection of SARS-CoV-2 by RT-PCR? Comparing saliva with oro-nasopharyngeal swabs

Abstract

Abstract The gold standard method in the diagnosis of SARS-CoV-2 infection is the detection of viral RNA in nasopharyngeal sample by RT-PCR. Recently, saliva samples has been suggested as an alternative due to being fast, reliable and non-invasive, rather than nasopharyngeal samples. We compared RT-PCR results in nasopharyngeal, oro-nasopharyngeal and saliva samples of COVID-19 patients. 98 of 200 patients were positive in RT-PCR analysis performed before the hospitalization. In day 0, at least one sample was positive in 67% of 98 patients. Positivity rate was 83% for both oro-nasopharyngeal and nasopharyngeal samples, while it was 63% for saliva samples ( p <0.001). On day 5, RT-PCR was performed in 59 patients, 34% had at least one positive result. The positivity rate was 55% for saliva and nasopharyngeal samples, while it was 60% for oro-nasopharyngeal samples. Our study shows that the sampling saliva does not increase the sensitivity of RT-PCR tests at early stages of infection. However, on 5th day, viral RNA detection rates in saliva were similar to nasopharyngeal and oro-nasopharyngeal samples. In conclusion, we suggest that, in patients receiving treatment, virus presence in saliva, in addition to the standard samples, is important to determine the isolation period and to control the transmission.