In contrast, a thermal cycler that does not have linear ramping technology heats at different rates throughout the ramping curve. There are two problems one can infer from this.
Firstly, the variable PCR ramp rate itself. Such temperature behavior can affect PCR results for systems that are sensitive to reaction speed, and it also makes it difficult to transfer a PCR program from one thermal cycler to another thermal cycler of a different brand, since there is no way to determine the exact ramp to follow.
For further reading: The paper Widespread use of incorrect PCR ramp rate negatively impacts multidrug-resistant tuberculosis diagnosis (MTBDRplus) published by Dr. Grant Theron’s group cautioned on the impact of ramp rate on PCR results.
Secondly, the actual ramp rate would be lower than published, which means the cycler is slower than what you would expect it to be (Table 1).
So, if your purpose behind getting a “fast cycler” is that you could finish a PCR faster, or run more PCRs, or free up the booking schedule so that it is more convenient for multiple users, then looking at the ramp rates specifications would not necessarily help you. In fact, it is rather misleading!
This is especially true even when referencing the “measured average ramp rate”. As this also might not reflect the actual runtimes of PCR protocols. In the example in Table 1, thermal cycler B has a higher measured average ramp rate than thermal cycler S but is obviously slower than thermal cycler S. This might be due to other factors that affect temperature behavior, such as degree of overshoot/ undershoot. Temperature control modes and/or reaction volume settings may also exert different degree of influence on ramping behavior of different thermal cyclers.
Hence, what you should really be looking at is the total PCR run time (Table 1) as this would be a better representation of speed.