Get Help Sign In

Frequently asked questions

Our Scientific Applications Support team has assembled a list of frequently asked questions to help you find answers quickly. Filter using one or more categories to focus on specific topics, or use the search bar to perform a text search.

When running qPCR experiments, what is the difference between quantification cycle (Cq) and threshold cycle (Ct)?

The cycle at which fluorescence from amplification exceeds the background fluorescence has been referred to as threshold cycle (Ct), crossing point (Cp), and take-off point (TOF) by different instrument manufacturers. But the term is now standardized by the MIQE guidelines as the quantification cycle( Cq). A lower Cq correlates with higher target expression in a sample.

Access the MIQE guidelines at:

Bustin SA, Benes V, et al. (2009) The MIQE Guidelines: minimum information for publication of quantitative real-time PCR experiments. Clin Chem, 55(4): 611−622. Updates: Bustin

SA, Beaulieu JF, et al. (2010) MIQE précis: Practical implementation of minimum standard guidelines for fluorescence-based quantitative real-time PCR experiments. BMC Mol Biol.11: 74–78, and Bustin SA, Benes V, et al. (2011) Primer sequence disclosure: A clarification of the MIQE Guidelines. Clin Chem, 57:919−921.