Figures in clinical trial reports: current practice & scope for improvement

Trials. 2007 Nov 19:8:36. doi: 10.1186/1745-6215-8-36.


Background: Most clinical trial publications include figures, but there is little guidance on what results should be displayed as figures and how.

Purpose: To evaluate the current use of figures in Trial reports, and to make constructive suggestions for future practice.

Methods: We surveyed all 77 reports of randomised controlled trials in five general medical journals during November 2006 to January 2007. The numbers and types of figures were determined, and then each Figure was assessed for its style, content, clarity and suitability. As a consequence, guidelines are developed for presenting figures, both in general and for each specific common type of Figure.

Results: Most trial reports contained one to three figures, mean 2.3 per article. The four main types were flow diagram, Kaplan Meier plot, Forest plot (for subgroup analyses) and repeated measures over time: these accounted for 92% of all figures published. For each type of figure there is a considerable diversity of practice in both style and content which we illustrate with selected examples of both good and bad practice. Some pointers on what to do, and what to avoid, are derived from our critical evaluation of these articles' use of figures.

Conclusion: There is considerable scope for authors to improve their use of figures in clinical trial reports, as regards which figures to choose, their style of presentation and labelling, and their specific content. Particular improvements are needed for the four main types of figures commonly used.