Re: Is the Risk Difference Really a More Heterogeneous Measure?

With great interest did we read the much-needed commentary by Poole et al.1 on the empirical evidence behind claims that the risk difference (RD) is more heterogeneous (i.e., the difference in effects between studies or groups of patients) than the odds ratio (OR). In their contribution, the authors show that the previously reported higher rejection rates of RD homogeneity may be explained by differences in power between measurement scales, an issue we previously addressed as well.2 Without detracting from their contribution or conclusions, with which we agree, we were surprised that the authors omitted the theoretical grounds why the OR is thought to be a less heterogeneous measure.