Scenario B: qPCR curves with similar threshold cycles can have different f-values. PCR amplification of the S27a transcript on the same RNA in two different duplicates, with the second duplicate set (blue and green line) obtained with only 70% of the polymerase concentration as in the first set (red and black line). The threshold cycle obtained from the second derivative maximum method was within 13.6 ± 0.3 cycles. Both insets depict the parameter estimates for 'f' and 'e' for the fitted curves, showing that these two parameters are highly correlated. Black circles indicate experimental measurements.
Spiess et al. BMC Bioinformatics 2008 9:221 doi:10.1186/1471-2105-9-221