Fig. 2: Positive specimens are detected after a 100-fold dilution.
From: A pooled testing strategy for identifying SARS-CoV-2 at low prevalence
a, b, Each of six typical SARS-CoV-2-positive specimens was diluted through pooling with 19, 49 or 99 negative specimens. A Ct value (that is, the PCR cycle at which the fluorescence signal generated by a specimen exceeds the baseline signal) was determined for each pool through RT–PCR amplification of the N (a) and orf1ab (b) genes of SARS-CoV-2. For each gene, the Ct values are plotted against the dilution factor. The red horizontal lines indicate the Ct value (40) at or below which a specimen is considered positive. All Ct curves stay below the red lines even if the positive specimens are diluted 100-fold (Extended Data Fig. 1 and Extended Data Table 2).
