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All trials require a compromise between including sufficient practitioners to recruit a representative cohort of patients and the time and cost of recruiting and maintaining the motivation of these practitioners. Prior beliefs relating to the efficacy and direct or side effects of an intervention affect both doctor and patient participation. Trials in any setting are rarely fully representative with respect to both patient and disease related characteristics. Modelling, sensitivity, analysis, and statistical estimates of uncertainty are necessary to determine the generalisability of trials and to particularise results to a given clinical setting. Trials in primary care should give more representative results and are preferable to applying results obtained in secondary care.

Original publication




Journal article


British Medical Journal

Publication Date





24 - 27