Requiring an amyloid-β(1-42 )biomarker may improve the efficiency of a study, and simulations may help in planning studies

A recent article by Schneider and colleagues has generated a lot of interest in simulation studies as a way to improve study design. The study also illustrates the foremost principal in simulation studies, which is that the results of a simulation are an embodiment of the assumptions that went into it. This simulation study assumes that the effect size is proportional to the mean to standard deviation ratio of the Alzheimer Disease Assessment Scale - cognitive subscale in the population being studied. Under this assumption, selecting a subgroup for a clinical trial based on biomarkers will not affect the efficiency of the study, despite achieving the desired increase in the mean to standard deviation ratio.