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. 1999 Feb;37(2):327–332. doi: 10.1128/jcm.37.2.327-332.1999

FIG. 1.

FIG. 1

Typical amplification plot. The graph of the increment of fluorescence reporter signal (ΔRn) versus cycle number during PCR shows three stages: baseline, exponential phase, and plateau. The CT value is calculated by determining the point at which the fluorescence exceeds an arbitrary threshold limit (usually 10 times the standard deviation of the baseline).