The aim of this paper is to describe the design features and practicalities of conducting a cluster randomized trial of obesity management in primary care. The aim of the trial is to assess the effectiveness of an obesity management educational intervention delivered to staff within primary care practices (unit of randomization) in terms of change in body weight of their patients (unit of analysis) at one year. The design features which merit particular attention in this cluster randomized trial include standardization of intervention, sample size considerations, recruitment of patients prior to randomization of practices, method of randomization to balance control and intervention practices with respect to practice and patient level characteristics, and blinding of outcome assessment. The practical problems (and our solutions) associated with implementing these design features, particularly those that result in a time delay between baseline data collection, randomization and intervention, are discussed.
OBJECTIVE: To evaluate a training programme intended to improve the management of obesity, delivered to general practice teams. DESIGN: Cluster randomised trial. SETTING: Northern and Yorkshire region of England. PARTICIPANTS: 44 general practices invited consecutively attending obese adults to participate; 843 patients attended for collection of baseline data and were subsequently randomised. INTERVENTION: 4.5 hour training programme promoting an obesity management model. MAIN OUTCOME MEASURES: Difference in weight between patients in intervention and control groups at 12 months (main outcome measure) and at 3 months and 18 months; change in practitioners' knowledge and behaviour in obesity management consultations. RESULTS: Twelve months after training the patients in the intervention group were 1 (95% confidence interval--1.9 to 3.9) kg heavier than controls (P = 0.5). Some evidence indicated that practitioners' knowledge had improved. Some aspects of the management model, including recording weight, target weight, and dietary targets, occurred more frequently in intervention practices after the training, but in absolute terms levels of implementation were low. CONCLUSION: A training package promoting a brief, prescriptive approach to the treatment of obesity through lifestyle modification, intended to be incorporated into routine clinical practice, did not ultimately affect the weight of this motivated and at risk cohort of patients.
The aim of this paper is to describe the design features and practicalities of conducting a cluster randomized trial of obesity management in primary care. The aim of the trial is to assess the effectiveness of an obesity management educational intervention delivered to staff within primary care practices (unit of randomization) in terms of change in body weight of their patients (unit of analysis) at one year. The design features which merit particular attention in this cluster randomized trial include standardization of intervention, sample size considerations, recruitment of patients prior to randomization of practices, method of randomization to balance control and intervention practices with respect to practice and patient level characteristics, and blinding of outcome assessment. The practical problems (and our solutions) associated with implementing these design features, particularly those that result in a time delay between baseline data collection, randomization and intervention, are discussed.
