Evaluation of different sample treatments options in a simple and safe procedure for the detection of SARS-COV-2 in saliva

Rubio, Camila P.; Franco-Martínez, Lorena; Resalt, Cristina Sánchez; Torres-Cantero, Alberto; Morata-Martínez, Irene; Bernal, Enrique; Alcaraz, María J.; Vicente-Romero, María R.; Martínez-Subiela, Silvia; Tvarijonaviciute, Asta; Cerón, José J.

Objectives To evaluate four sample treatments in a safe and simple procedure for SARS-CoV-2 detection in saliva. Methods Four sample treatments in three-step procedure for the detection of SARS-CoV-2 in saliva, consisting in 1) heating at 95 °C during 5 minutes for sample inactivation, 2) sample treatment, and 3) analysis by RT-LAMP were evaluated using saliva samples with known amounts of added viral particles and saliva from infected individuals. Results Three treatments had a limit of detection of 500.000 viral particles per ml of saliva and could have a practical use for detecting those individuals that potentially could transmit the disease. The treatment consisting of a combination of phosphate buffer, dithiothreitol, ethylenediaminetetraacetic acid and proteinase K, and an additional 95 °C heating yielded the lower LOD 95 and the sensitivity ranged from 100% in patients with RT-PCRs NPS of Ct<20 to 47.8% in patients with Cts>30. Conclusions This report highlights the importance for an adequate sample treatment in saliva for the detection of SARS-CoV-2 and describes a cheap and flexible procedure that can be adapted to-point-of-care and, although its sensitivity is lower than RT-PCRs, can contribute to the Covid-19 control by the detection of individuals able to transmit the disease.