A Scalable Saliva-based, Extraction-free RT-LAMP Protocol for SARS-Cov-2 Diagnosis

Asprino, P.; Bettoni, F.; Camargo, A.; Coelho, D.; Coppini, G.; Correa, I.; Freitas, E.; Inoue, L.; Kitajima, J. P.; Kuroki, M.; Masotti, C.; Marques, T.; Reis, A.; Reis, L. F.; Santos, B.; dos Santos, E.; Schlesinger, D.; Sena, C.; Spadaccini, T.; Taniguti, L.

Scalable, cost-effective screening methods are an essential tool to control SARS-CoV-2 spread. We have developed a straight saliva-based, RNA extraction-free, RT-LAMP test that is comparable to current nasopharyngeal swab RT-PCR tests in both sensitivity and specificity. Using a 2-step readout of fluorescence and melting-point curve analysis, the test is scalable to more than 30,000 tests per day with average turnaround time of less than 3 hours. The test was validated using samples from 244 symptomatic patients, and showed sensitivity of 78.9% (vs. 85.5% for nasopharyngeal swabs RT-PCR) and specificity of 100% (vs. 100% for nasopharyngeal swabs RT-PCR). Our method is therefore accurate, robust, time and cost effective and therefore can be used for screening of SARS-CoV-2.