Efficient high throughput SARS-CoV-2 testing to detect asymptomatic carriers

Noam Shental; Shlomia Levy; Shosh Skorniakov; Vered Wuvshet; Yonat Shemer-Avni; Angel Porgador; Tomer Hertz

Since our proof-of-concept experiments used samples from positive individuals that were previously identified, we observed an additional 5-cycle drop in PCR sensitivity that was likely caused by RNA degradation of samples following freeze-thaw cycles. To confirm this, we tested several individual samples before and after a freeze-thaw cycle and observed a similar drop in PCR sensitivity. However, P-BEST was still able to correctly identify all positive subjects within each of the sample sets. We note that this reduction will not occur when P-BEST will be implemented on fresh samples collected directly into lysis buffer, per our current experimental protocol. To further address the sensitivity issues we propose to (1) modify the sample collection protocol to collect samples directly into lysis buffer, thereby increasing the initial concentration of RNA in the collected samples; and (2) Test P-BEST pooled samples using the SeeGene SARS-CoV-2 PCR kit, that also includes primers for the NP SARS-COV-2 gene, which in our preliminary experiments had higher sensitivity as compared to the other genes included in the kit, and was positive even when diluting a single positive sample into a pool of 120 subjects (Supplemental Figure 1A) .