FIG 1.
Crossing point (Cp) values of RT-PCR and result of cell culture in asymptomatic SARS-CoV-2 carriers, according to number of days since SARS-CoV-2 infection diagnosis by PCR of nasopharyngeal swabs. Red dots indicate samples in which cytopathic effect (CPE) was observed, and black dots represent culture-negative samples. Triangles connected with a dotted line correspond to samples obtained from Carrier_1. With fluorescence-based real-time PCR, the number of cycles at which fluorescence signal from amplification exceeds the background fluorescence level is determined as the crossing point, threshold cycle (CT), or other values by different instrument manufacturers. While there are differences in how they are calculated, they are considered biologically equivalent in that a lower value correlates with a higher copy number of the target nucleotide sequence.