Publications

Clinical trials are often stopped prematurely by Data and Safety Monitoring Boards, sponsors, or the investigators for reasons such as unexpected harmful effects of the intervention, clear lack of benefit, or futility due to sluggish recruitment or an unexpectedly low outcome rate in the placebo group. Planning for closeout, however, usually does not begin until after the trial is well underway. This article describes the experience of the Heart and Estrogen/progestin Replacement Study (HERS) investigators when data from the first year of follow-up revealed a clear but non-significant divergence in outcome rates between the treatment groups, and planning for early closure was initiated. Three advantages of beginning early to plan for closeout are described and approaches to planning closeout are suggested.

Antimalarial clinical trials use genotyping techniques to distinguish new infection from recrudescence. In areas of high transmission, the accuracy of genotyping may be compromised due to the high number of infecting parasite strains. We compared the accuracies of genotyping methods, using up to six genotyping markers, to assign outcomes for two large antimalarial trials performed in areas of Africa with different transmission intensities. We then estimated the probability of genotyping misclassification and its effect on trial results. At a moderate-transmission site, three genotyping markers were sufficient to generate accurate estimates of treatment failure. At a high-transmission site, even with six markers, estimates of treatment failure were 20% for amodiaquine plus artesunate and 17% for artemether-lumefantrine, regimens expected to be highly efficacious. Of the observed treatment failures for these two regimens, we estimated that at least 45% and 35%, respectively, were new infections misclassified as recrudescences. Increasing the number of genotyping markers improved the ability to distinguish new infection from recrudescence at a moderate-transmission site, but using six markers appeared inadequate at a high-transmission site. Genotyping-adjusted estimates of treatment failure from high-transmission sites may represent substantial overestimates of the true risk of treatment failure.