[Enriched-enrollment randomized-withdrawal trials]

Abstract

A clinical trial's power depends on the probability of observing an effect of the tested drug in the trial population, on the size of this effect, and on the heterogeneousness of the judgment criterion in the population. Enriched-enrollment randomized-withdrawal trials are clinical trials which comprise a first period in which subjects are selected depending on whether they respond to the tested drug or not. The responding patients are subsequently randomized into 2 groups: in one of them the treatment is pursued, in the other group a placebo is substituted. These designs are very useful in pediatrics, decreasing the number of subjects needed, on condition that the effect of the treatment is only suspensive in a setting of chronic disease. Here we discuss the advantages and disadvantages of such trials.