Table 4.

RT-LAMP limit of detection in saliva samples carried out on a Sentinel instrument in a clinical pathology laboratory.

Six SARS-CoV-2 saliva samples with different viral loads were serially diluted 1:10 in nuclease-free water down to 1:100,000 dilutions to obtain 36 samples with a wide range of Ct values. The diluted samples were further diluted 1:3 in Vitro Diagnostica Saliva Transport buffer M (VTM) and heat inactivated for 10 min at 95 °C. Direct RT-PCR (Seegene Allplex) was carried out with 5 µl of heat-treated saliva dilution in VTM; NEB colorimetric RT-LAMP (N&E-gene, M1800 2 × LAMP mix) was carried out on a Sentinel station with 3 μl of the same template as RT-PCR. Table A shows the results of RT-PCR and RT-LAMP for all 36 saliva samples organized by sample. Table B shows the same data organized by Ct value. Table B clearly demonstrates that all saliva samples up to a Ct of 31.1 were detected by RT-LAMP. Samples with higher Ct values started showing stochastic signals, indicating that the limit of detection for VTM/heat-treated saliva samples combined with NEB M1800/N&E chemistry is above a Ct of 31.