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.