Improved RT-PCR SARS-Cov2 results interpretation by indirect determination of cut-off cycle threshold value

ABSTRACT Clinical laboratories of the developing world are overwhelmed with RT-PCR SARS-Cov2 testing demands. It is of paramount importance that each clinical laboratory use an appropriate cut-off value in the interpretation of SARS-Cov2 real-time RT–PCR results, which is specific to their laboratory performances as ISO 15189 recommendations stipulate. We applied an indirect statistical method to a large mixed data set of Ct values (ORF1ab and N) to estimate cut-off Ct value (∼32 cycles).we conclude that the use of indirect statistical approaches to estimate cut-off value in the interpretation of SARS-Cov2 real-time RT–PCR results may improve differential diagnosis of COVID-19 cases with low risk of infectivity, and may help to better estimates of the burden of COVID-19 disease.