A Practical Guide to Cluster Randomised Trials in Health Services Research

Preface xiii Notation xv Table of cases: Trials used as examples in more than one chapter in the book xviii 1 Introduction 1 1.1 Introduction to randomised trials 2 1.2 Explanatory or pragmatic trials 2 1.3 How does a cluster randomised trial differ from other trials? 3 1.4 Between-cluster variability 9 1.5 Why carry out cluster randomised trials? 10 1.6 Quality of evidence from cluster randomised trials 13 1.7 Historical perspectives 16 1.8 Summary 18 References 19 2 Recruitment and ethics 22 2.1 Selecting clusters and participants to enhance external validity 22 2.2 Ethics of cluster randomised trials 24 2.3 Selection and recruitment of participants to enhance internal validity 35 2.4 Retention of participants in the trial 41 2.5 Summary 41 References 41 3 Designing interventions 44 3.1 Lack of effectiveness of interventions evaluated in cluster randomised trials 45 3.2 What is a complex intervention? 46 3.3 Phases in the development of a complex intervention 50 3.4 Identifying evidence for potential intervention effect (pre-clinical phase) 50 3.5 Understanding more about intervention components (modelling phase) 53 3.6 Developing the optimum intervention and study design (exploratory trial phase) 55 3.7 What is the intervention? 57 3.8 Summary 58 References 58 4 Pilot and feasibility studies 60 4.1 What is a pilot study? 60 4.2 Reasons for conducting pilot and feasibility studies 63 4.3 Designing a pilot or feasibility study 69 4.4 Reporting and interpreting pilot studies 71 4.5 Summary 72 References 73 5 Design 74 5.1 Parallel designs with only two arms 75 5.2 Cohort versus cross-sectional designs 85 5.3 Parallel designs with more than two arms 88 5.4 Crossover designs 92 5.5 Further design considerations 95 5.6 Summary 96 References 96 6 Analysis 99 6.1 Data collection and management 99 6.2 Analysis - an introduction 101 6.3 Analyses for two-arm, completely randomised, stratified or minimised designs 104 6.4 Analyses for other designs 124 6.5 Intention to treat and missing values 129 6.6 Analysis planning 131 6.7 Summary 132 References 133 7 Sample size calculations 137 7.1 Factors affecting sample size for cluster randomised designs 138 7.2 Calculating sample size using the intra-cluster correlation coeffi cient 142 7.3 Sample size calculations for rates 145 7.4 Restricted number of clusters 146 7.5 Trials with a small number of clusters 149 7.6 Variability in cluster size 150 7.7 Comparison of different measures of between-cluster variability 154 7.8 Matched and stratifi ed designs 160 7.9 Sample size for other designs 166 7.10 Summary 169 References 169 8 The intra-cluster correlation coeffi cient 172 8.1 What is the ICC? 173 8.2 Sources of ICC estimates 175 8.3 Choosing the ICC for use in sample size calculations 179 8.4 Calculating ICC values 185 8.5 Uncertainty in ICCs 192 8.6 Summary 193 References 193 9 Other topics 196 Richard Grieve 9.1 Systematic reviews 197 9.2 Cost effectiveness analyses 207 9.3 Process evaluation 212 9.4 Monitoring 213 9.5 Summary 215 References 215 10 Trial reporting 218 10.1 Trial quality and reporting quality 218 10.2 Steps to improve trial reporting in the early stages of the trial 227 10.3 Reporting randomised trials in journal and conference abstracts 230 10.4 Application of CONSORT statement to cluster randomised trials 232 10.5 Summary 262 References 263 Index 267