Percent change can be extremely misleading for a number of reasons (e.g. regression to the mean), even though in the medical literature percent change is used quite frequently to "normalize" clinical data. In a regression model it is better to put the baseline value in the overall model, as opposed to transforming the data to "percent change".
However, I'm trying to understand what pitfalls one might encounter if you use percent change in power calculations for prospective studies.
Is it better to use absolute values for power calculations? Would using percent change lead to erroneous calculations the same way it would for normalizing clinical data?