Optimizing SARS-CoV-2 molecular diagnostic using N gene target: insights about reinfection

Contelli Klein, R.; Fabres Klein, M. H.; Barbosa, L. G.; Knnup, L. V. G.; Venancio, L. P. R.; Berlink Lima, J.; Araujo-Santos, T.

Abstract Introduction: Molecular diagnosis of SARS-CoV-2 is a huge challenge to many countries around the world. The cost of tests to check infected people is inaccessible since specialized teams and equipment are not disposable in remote locations. Herein, we compared the fitness of two primers sets to the SARS-CoV-2 N gene in the molecular diagnosis of COVID-19. Materials and Methods: The 1029 patient samples were tested to presense/abscence molecular test using in house US CDC protocol. We compared the fitness of two primers sets to two different regions of N gene targets. Results: Both targets, N1 and N2 displayed similar fitness during testing with no differences between Ct or measurable viral genome copies. In addition, we verified security ranges Cts related to positive diagnostic with Ct above 35 value failuring in 66,6% after retesting of samples. Main conclusion: Our data suggest that it is secure to use just one primer set to the N gene to identify SARS-CoV-2 in samples and the labs should be careful to set positive samples in high Ct values using high cutoffs. Keywords: Diagnostic, SARS-CoV-2, COVID-19, N gene, Reinfection