Threshold Cycle (Ct)

The Threshold Cycle (Ct) is a value used in PCR (Polymerase Chain Reaction) testing to measure how much of a specific genetic material, like DNA or RNA, is present in a sample. During PCR, the genetic material is copied repeatedly until it reaches a detectable level. The Ct is the cycle number at which this detectable level is first reached. A lower Ct indicates a higher amount of the target material in the sample, meaning the genetic material was present in larger quantities initially. Conversely, a higher Ct suggests less of the target was present.