an overview of how such a trial might be designed and the operational, logistical, and ethical issues that might arise.

TRIAL DESIGN FEATURES

In a community randomized trial, some communities receive certain added interventions while other communities awaiting such interventions serve as comparison sites (often called “controls”). A stepped-wedge design would be most appropriate for a community randomized trial of multi-component HIV prevention programs. This design involves sequential rollout of an intervention (whereby intervention components are added to a standard package) in participating communities over time. Areas that are yet to receive a specific intervention serve as controls for the intervention area(s). This design is particularly relevant where an intervention may do more good than harm (making a factorial design, in which certain participants do not receive the intervention, unethical). Such a design is also appropriate where, for logistical, practical, or financial reasons, a program cannot simultaneously deliver an intervention to all participants (Gambia Hepatitis Study Group, 1987).

A community randomized trial makes particular sense for injecting drug users because they may share the same drug-using network and compare their treatment experiences. Thus randomizing participants on an individual basis could create situations where the control group could not be insulated from the intervention group, potentially contaminating the control regimen and blunting the study’s ability to detect important differences.

The multi-national, multi-site design feature of the community randomized trial is appropriate for several reasons. First, the burden on individual research sites in implementing a large trial across many communities with sufficient HIV incidence to evaluate interventions is high. Spreading the sample across many sites reduces the burden for a particular research group.

Second, implementing the study at numerous sites allows investigators to evaluate whether the interventions work in different communities. While the interventions would need to be tailored somewhat to the local context, this has proven feasible in trials of similar complexity. The National Institutes of Mental Health (NIMH) Collaborative HIV/STD Prevention Trial is a good example of a multi-national, multi-site community randomized trial. Funded by the National Institutes of Health, the study relies on local public opinion leaders to promote HIV testing and counseling and encourages risk reduction in five developing countries: China, India, Peru, Russia, and Zimbabwe (RTI International, 2005).

Third, using multiple sites increases the statistical power of the study. Because participants within one community are likely to have similar out-



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