tailieunhanh - Ebook Designing clinical research (3/E): Part 2

(BQ) Part 2 book “Designing clinical research” has contents: Alternative trial designs and implementation issues, designing studies of medical tests, utilizing existing databases, addressing ethical issues, designing questionnaires and interviews, data management, community and international studies, and other contents. | 11 Alternative Trial Designs and Implementation Issues Deborah Grady, Steven R. Cummings, and Stephen B. Hulley In the last chapter, we discussed the classic randomized, blinded, parallel group trial: how to select the intervention, choose outcomes, select participants, measure baseline variables, randomize, and blind. In this chapter, we describe alternative clinical trial designs and address the conduct of clinical trials, including interim monitoring during the trial. ALTERNATIVE CLINICAL TRIAL DESIGNS Other Randomized Designs There are a number of variations on the classic parallel group randomized trial that may be useful when the circumstances are right. The factorial design aims to answer two (or more) separate research questions in a single cohort of participants (Fig. ). A good example is the Women’s Health Study, which was designed to test the effect of low-dose aspirin and vitamin E on risk for cardiovascular events among healthy women (1). The participants were randomly assigned to four groups, and two hypotheses were tested by comparing two halves of the study cohort. First, the rate of cardiovascular events in women on aspirin is compared with women on aspirin placebo (disregarding the fact that half of each of these groups received vitamin E); then the rate of cardiovascular events in those on vitamin E is compared with all those on vitamin E placebo (now disregarding the fact that half of each of these groups received aspirin). The investigators have two complete trials for the price of one. The factorial design can be very efficient. For example, the Women’s Health Initiative randomized trial was able to test the effect of three interventions (hormone therapy, low-fat diet and calcium plus vitamin D) on a number of outcomes in one cohort (2). A limitation is the possibility of interactions between the effects of the treatments on the outcomes. For example, if the effect of aspirin on risk for cardiovascular disease is different in women .