Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘Table 5. Main advantages and disadvantages of cluster randomized trials.Advantages• Optimal design for evaluating quality improvementstrategies in health care intervention and educationprogram studies• Account for contamination between patientswithin a cluster• Easier to administrate the randomization and centersDisadvantages• Larger sample size is required than fora simple randomized trial• The patients and clinicians may recognizewhether they are in the active or placebo arm• Clinicians might transfer informationbetween clustersIssues related to the nature and practice of informed consent in CRTs raisenew questions that need to be properly addressed. Other ethical implications ofthese trials, such as principles relating to the quality of the scientific design andanalysis, balance of risk and benefit, liberty to leave a trial, early stopping of atrial, and the power to exclude people from potential benefits, also need carefulconsideration [20].Advantages and limitations of using clusterrandomized trials in clinical researchCRTs represent an important type of design that can be consideredcomplementary to conventional randomized trials. CRTs have certain advantagesover conventional randomized trials. For instance, CRTs help to account for thepotential for contamination between treatments when trial patients are managedwithin the same setting. Moreover, the outcomes of patients in a cluster are likelyto be influenced by a number of similar factors. Thus, these patients cannot betreated as having independent outcomes on an individual basis. CRTs areespecially useful for evaluating quality improvement strategies in health careinterventions and education programs.On the other hand, when choosing a design between individual randomized trialsand CRTs, one should be ready for some trade-off due to the limited efficiency ofCRTs. There is potentially a considerable loss of power between a conventionalrandomized controlled trial and a CRT for the same number of patients.Therefore, in the statistical analysis and estimation of trial power, the clusteringaspect of the design should not be ignored. Some main points about CRTsdiscussed in this chapter are summarized in Table 5.149