I understand that there are two ways to determine the Ct value. What are they?

The Ct value can be determined by two different methods:

1. The crossing point method defines the Ct value as the crossing point between the amplification curve and the threshold line.
2. The second derivative maximum method defines the Ct value as the point of the maximum of the second derivative of amplification curve (second differential curve).

The latter method allows highly precise analyses, since the Ct value is fixed by setting a threshold and is not subject to the effect of instrument-specific detection variability.
Please note that some instrument systems do not allow one to choose between the crossing point method and the second derivative maximum method

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