A randomized controlled trial or randomized control trial. A cluster randomized trial crt is a trial in which individuals are randomized in groupsthe group as a whole is randomized and not the individual. Cluster randomized trials, now in its second edition, has become a standard text on this important method, which is increasingly used in clinical and public health. In this case, the lack of independence among individuals in the same cluster, i. Use of clustering analysis in randomized controlled trials in.
Whilst a well conducted individually randomised controlled trial rct is the gold standard for assessing the. A key property of cluster randomization trials is that inferences are frequently intended to apply at the individual level while randomization is at the cluster or group level. The book on cluster randomization by murray 1998 is called the design and analysis of grouprandomized trials. I find it particularly useful in designing and analyzing studies to evaluate different effects of vaccination. The result has been poor standards of design, analysis and reporting, which this book seeks to rectify by providing researchers with a unified account of the issues particular to cluster randomized trials. In a cluster randomized trial, study participants are randomized in groups or clusters so that all members within a single group are assigned to either the experimental intervention or the control. Cluster randomised controlled trials are also known as cluster randomised trials, grouprandomised trials, and placerandomized trials a 2004 bibliometric study documented an increasing number of publications in the medical literature. Cluster randomised controlled trials are also known as cluster randomised trials, 2 grouprandomised trials, 3 4 and place randomized trials. A cluster randomization trial is one in which intact social units, or clusters of individuals, are randomized to different intervention groups.
Cluster randomized trials have become an important, and in many cases, the key methodology for assessing the impact of public health interventions, especially for infectious diseases. I always mention dont do a cluster randomized trial if you dont have to, and i emphasize do not do a cluster randomized trial for convenience or ease. Because each cluster then provides only one data point, the data can be considered to be independent, allowing standard statistical tests to be used. Cluster randomised trials interdisciplinary statistics. The traditional approach to the analysis of cluster randomized trials has been to calculate a summary measure for each cluster, such as a cluster mean or proportion. Dec 15, 2016 the healthy lifestyles programme help trial is being conducted to determine whether a novel schoolbased intervention is effective and costeffective in preventing obesity in 910 yearold children. Group randomized also known as cluster randomized trials are those trials where the unit of randomization is one of the several types of groups rather than an individual. Grouprandomized trials grts are comparative studies designed to evaluate interventions that operate at a group level, manipulate the physical or social environment, or cannot be delivered to individuals. Stoney, laura lee johnson, in principles and practice of clinical research fourth edition, 2018. Jan 12, 2009 cluster randomised trials discusses the design, conduct, and analysis of health trials that randomise groups of individuals to different treatments. Recognize when cluster randomization should be preferred to individual randomization. Trials randomizing clusters have become particularly widespread in the evaluation of nontherapeutic interventions, including lifestyle modification, educational programmes and innovations in the provision of health care. Avoiding unnecessary mathematical detail, the book covers basic concepts underlying the. A number of innovations have been developed recently.
Physicians, group practices, health plans, or even geographic regions counties or states can be defined as clusters. Design and analysis of cluster randomization trials in. For example, clusters may be clinical practices or schools where. The method of randomization for clusterrandomized trials. Cluster randomised trials evidencebased management. The first chapter sets out the questions trial designers should ask themselves when considering whether or not to randomize by cluster. Cluster randomised trials covers the design, analysis, and conduct of health intervention trails in which groups or clusters of individuals are randomized to different conditions. Cluster randomized trials crts differ from individually randomized rcts in that the unit of randomization is something other than the individual participant or patient. Recommendations cluster randomized trial crt designs are frequently used in human subjects research. Division of clinical trials and epidemiological sciences, national cancer centre singapore, 11 hospital drive, singapore 16910, singapore. Cluster trials, however, randomize interventions to groups of patients e. Cluster randomization trials, in which intact groups of individuals are randomized to receive different interventions, have been increasingly adopted by public health researchers over the past 2 decades after publication of a seminal article by cornfield1 and the extensive methodological developments stimulated by this article.
It explores the advantages of cluster randomization, with special attention given to evaluating the effects of interventions against infectious diseases. Cluster randomization trials, in which intact groups of individuals are randomized to receive different interventions, have been increasingly adopted by public health researchers over the past 2 decades after publication of a seminal article by cornfield 1 and the extensive methodological developments stimulated by this article. Cluster randomised trials are trials in which groups or clusters of individuals are randomly allocated to different forms of treatment. The principle features of this extension include recommendations to.
The cluster randomized trial crt is used increasingly in knowledge translation research, quality improvement research, community based intervention studies, public health research, and research in developing countries. The book covers multiple types of trials, including cluster randomized trials, multisite trials, individually randomized group treatment trials, and longitudinal intervention studies. Ethical issues posed by cluster randomized trials in health. Cluster randomised trials in the medical literature.
It explores the advantages of cluster randomization, with special attention given to evaluating the. The healthy lifestyles programme help trial is being conducted to determine whether a novel schoolbased intervention is effective and costeffective in preventing obesity in 910 yearold children. In health care, these trials often compare different ways of managing a disease or promoting healthy living, in contrast to conventional randomised trials which randomise individuals to different treatments, classically comparing new drugs with a placebo. Cluster randomised controlled trials are also known as cluster randomised trials, grouprandomised trials, and place randomized trials. Cluster randomized trials in health care research textbook.
These trials present unique issues of regulatory application. Cluster randomised trials pragmatic clinical trials unit. Ive set a seed in case youd like to recreate the results shown here and indicate the. Division of clinical trials and epidemiological sciences, national cancer centre. It explores the advantages of cluster randomisation, with special attention given to evaluating the effects of interventions against infectious diseases. This work is licensed under a creative commons attribution. The units of randomization for such trials are diverse, including. A short summary of what the book offers is provided in regards to these topics. Cluster randomized trials, now in its second edition, has become a standard text on this important method, which is increasingly used in clinical and public health science. With an emphasis on key concepts rather than mathematical details, the book uses case studies to illustrate methods and stata code based on realworld datasets to. Cluster randomized trials rethinking clinical trials.
Crts are in common use in areas such as education and public health research. Use of clustering analysis in randomized controlled trials. In cluster randomized trials, smd more complex in cluster randomized trials, we have clusters such as schools or clinics randomized to treatment and control we have at least two means. This article describes the detailed statistical analysis plan for the help trial, including an amendment and rationale for amendment made to originally planned sensitivity analyses. Assuming an average cluster size, required sample sizes are readily computed for both binary and continuous outcomes, by estimating a design effect or inflation factor.
An analysis of variance pitfall the fixed effect analysis in a nested design. It also offers insight on choosing which trial is best suited to a given project. Cluster randomized trials are trials that randomize clusters of people, rather than individuals. Moulton estimated delivery 312 business days format hardcover condition brand new there is an increasing need for new health interventions to be rigorously evaluated through randomized controlled trials, which have become the gold standard for intervention studies. The wellknown consort statement for individually randomized trials begg et al. Cluster randomised trials is an extraordinarily practical book for anyone designing or analyzing clusterrandomized studies, covering both concepts and technical material with great clarity. The cluster randomized trial crt is the gold standard for evaluating the effectiveness of medical interventions. Cluster randomized trial an overview sciencedirect topics. A cluster randomised trial crt is a randomised controlled trial in which preexisting groups, called clusters, of individuals are randomly allocated to treatment arms. The effects of clustering in randomized controlled trials rcts and the resulting potential violation of assumptions of independence are now well recognized. Cluster randomised controlled trials crcts, in which clusters of individuals are randomised to intervention groups, are frequently used in the evaluation of service delivery interventions, primarily to avoid contamination but also for logistic and economic reasons. The purpose of these recommendations is to address the application of hhs and fda.
When patients in a single study are treated by several therapists, there is good reason to suspect that the variation in outcome will be smaller for patients treated in the same group than for patients treated in different groups. Avoiding unnecessary mathematical detail, the book covers basic concepts underlying the use of cluster randomisation, such as direct, indirect, and total effects. Jun 30, 2011 cluster randomised controlled trials crcts are frequently used in health service evaluation. And since variability of the outcome affects sample size, each approach has implications for sample size. This book is intended as a practical guide, written for researchers from the health professions including doctors, psychologists, and allied health professionals, as well as statisticians involved in the design, execution, analysis and reporting of cluster randomised trials. A practical guide to cluster randomised trials in health. Jan 12, 2012 this book is intended as a practical guide, written for researchers from the health professions including doctors, psychologists, and allied health professionals, as well as statisticians involved in the design, execution, analysis and reporting of cluster randomised trials. Pragmatic clinical trials unit about us methodological strengths and research cluster randomised trials. Simulation of each design just to be clear about these different randomization designs, ill simulate 1500 students using each. A 20 minute introduction to cluster randomised trials.
Vetter, roger chou, in practical management of pain fifth edition, 2014. Thus the unit of randomization may be different from the unit of analysis. In the statistical theory of design of experiments, randomization involves randomly allocating the experimental units across the treatment groups. Pitfalls of and controversies in cluster randomization trials.
The main attraction of pairmatching on strongly predictive baseline risk factors is the potential increase it brings in statistical efficiency and trial power. This book by richard hayes and lawrence moulton has become the leading methodological text in this area. The book describes in detail the aspects of crt designs and the analysis of data from such trials. The cluster randomized crossover crxo design is gaining popularity in trial settings where individual randomization or parallel group cluster randomization is not feasible or practical.
Analysis of cluster randomized trials in primary care. Types of trials individually randomized trials eligible individuals are randomized conventional medical rcts and many behavioral rcts selfselection of persons volunteering for enrollment cluster randomized trials clusters e. However, where the number of clusters are fixed in advance, but where it is possible to increase the number of individuals within. Introduction and scope cluster randomised trials crts are becoming increasingly important in health technology assessment. As a search of journals, this also misses the important book by donner a, klar n.
Crt designs are used not only to evaluate group interventions but also individual interventions where group level effects are relevant. Store search search title, isbn and author cluster randomised trials by richard j. For example, if an experiment compares a new drug against a standard drug, then the patients should be allocated to either the new drug or to the standard drug control using randomization. The research topics included in this volume are diverse. In the time since the publication of the first edition, the use of cluster randomised trials crts has increased substantially, which is reflected in the updates to this edition. Sample size calculations for cluster randomised controlled. Understand the statistical implications of cluster randomi zation. Group randomized trials grts are comparative studies designed to evaluate interventions that operate at a group level, manipulate the physical or social environment, or cannot be delivered to individuals. Sachrp recommendations on regulatory issues in cluster randomized studies approved october 26, 2016 executive summary. This design requires members of a pair stratum to be first matched o n known risk factors for outcome, with each member. The book describes in detail the aspects of crt designs and the analysis of.
In a crxo trial, not only are clusters of individuals rather than individuals themselves randomized to trial arms, but also each cluster participates in each arm of the trial at least once in separate periods. This book uses case studies to illustrate read more. Clustered randomized trials and the design effect rbloggers. Rct is a type of scientific often medical experiment that aims to reduce certain sources of bias when testing the effectiveness of new treatments. Power analysis of trials with multilevel data 1st edition. Ethical issues posed by cluster randomized trials in. Design and analysis of cluster randomization trials in health. However, cluster trials raise difficult ethical issues that challenge researchers, research ethics committees, regulators, and sponsors as they seek to fulfill responsibly. Exploring significant dimensions of place randomized trials also called cluster randomized trials or group randomized trials, these papers shed light on recent efforts to enhance the quality of designing such trials as well as on results reporting. But it turns out that the variability of the intervention effect depends entirely on how we randomize.
Cluster randomised trials discusses the design, conduct, and analysis of health trials that randomise groups of individuals to different treatments. Cluster randomised trials, second edition discusses the design, conduct, and analysis of trials that randomise groups of individuals to different treatments. The use of the cluster randomized crossover design in. A cluster randomised controlled trial is a type of randomised controlled trial in which groups of subjects as opposed to individual subjects are randomised. The main issue associated with their design, conduct, analysis, and interpretation, compared with individually randomized trials, is that two different units of measurementthe cluster and the patient. Computing effect sizes for clustered randomized trials. This book is an absolute essential for any scientist who is involved in the design, analysis or interpretation of such trials. Jul 04, 2011 store search search title, isbn and author cluster randomised trials by richard j. Cluster randomized trials crt in which the unit of randomization is a group of participants 3,4, or cluster are relevant for interventions applied at the level of the group, and may offer some advantages in trials enrolling participants with mcc. Reporting reporting of cluster randomization trials.