Patricia Yudkin

The need for clear comparisons We studied 169 randomised trials of non-drug interventions in primary care published between 1999 and 2003. We searched Medline, PSIQInfo, Bioabstracts, and Embase using the free text search terms “randomised controlled trials” and “primary care” and their synonyms, and excluding the term “placebo” appearing in the title or abstract; we also hand searched reference lists of retrieved papers. In many of these papers the interventions were incompletely described. We identified three principal problems: identifying the different components of the intervention, establishing the time at which components were delivered, and defining the differences between intervention arms. To clarify these aspects we suggest that it would be helpful to depict the experimental and control interventions graphically. The proposed graph is similar to a flowchart, with each treatment arm represented in a specific column, and with all the intervention components presented within that column. The time scale of the trial runs from top to bottom on the left hand side, with the times of randomisation and outcome measurement (or measurements) clearly marked. Each component of an intervention is depicted separately. Components delivered concurrently are displayed side by side, while those delivered consecutively are shown one beneath the other. We regard components either as objects or activities. Objects are represented by squares (to reflect their fixed nature) and activities by circles (to reflect their flexibility). Different components are labelled with different letters. Below the diagram, a legend gives a brief description of each component, including its form, content, functions, and details of who delivers it. If necessary, additional material can be given in the text. This approach will convey as much information as a written description, will clarify the basic structure of the experimental intervention, and elucidate the differences between treatment arms, as the examples below show.

Few studies have investigated abstinence beyond three years among participants who stop smoking during trials of nicotine replacement therapy,1–3 and even fewer have followed up smokers who failed to quit during such trials. We carried out an eight year follow up of people who had participated in a randomised controlled trial of the nicotine patch. Participants were the 1686 patients from general practices in Oxfordshire who took part in a double blind randomised controlled trial of the patch in 1991-2.4 5 At entry they smoked≥15 cigarettes a day and were aged 25–64 years. Participants wore the patches for 12 weeks. The main outcome was abstinence from smoking for one year, confirmed at 12, 24, and 52 weeks by a salivary cotinine concentration≤20 ng/ml (89% of cases) or expired carbon monoxide≤10 ppm (11%). In 1999-2000, we contacted 1532 of the 1625 living participants. We …

Many of the difficulties encountered in the design, organization and analysis of cluster randomized trials arise from the dual nature of such trials; that is, they focus on both the cluster and the individual. A trial now in progress to compare three methods of promoting secondary prevention of coronary heart disease in primary care includes only 21 general practices, but 2142 patients, and thus contains the problems of both small and large samples. With only seven practices in each arm, the trial demanded carefully restricted randomization, may be difficult to analyse, and risks loss of power if one practice should drop out. At the same time, the large number of patients makes for an expensive and administratively complex study. The simultaneous demands of clarity and thoroughness point to an analysis at both cluster and individual level. With two different approaches, however, there may be difficulties of presentation, even if the results agree, and additional problems of interpretation if they do not. Finally, practical considerations may conflict with theoretical demands. Since the trial contained a service element, all patients with heart disease had to be included, even though it would have been more efficient to take only a sample of patients from some practices. Copyright © 2001 John Wiley & Sons, Ltd.