Introduction Communicating the prognosis of a condition, either with or without treatment, can facilitate informed decision-making. This study investigated whether a bar graph, pictograph, or line graph was superior to text-only for communicating prognosis and whether differences existed between different graphs.

Methods Two online four-arm parallel-group randomised controlled trials. Statistical significance was set at p<0.016 to allow for three primary comparisons. Two Australian samples were recruited from members registered at Dynata online survey company. Trial A communicated prognostic information about an acute condition (acute otitis media) and trial B about a chronic condition (lateral epicondylitis). 417 and 433 participants in trials A and B respectively were analysed. In each trial four visual presentations were tested: bar graph, pictograph, line graph and text-only. Comprehension (scored 0–6) was the main outcome. Secondary outcomes included decision intention, presentation satisfaction and preferences.

Results In both trials, the mean comprehension score was 3.7 for the text- only group. None of the visual presentations were superior to text-only. In trial A, the adjusted mean difference (MD) compared with text-only was: 0.19 (95% CI -0.16 to 0.55) for bar graph, 0.4 (0.04 to 0.76) for pictograph and 0.06 (-0.32 to 0.44) for line graph. In trial B, the adjusted MD was: 0.1 (-0.27 to 0.47) for bar graph), 0.38 (0.01 to 0.74) for pictograph and 0.1 (-0.27 to 0.48) for line graph. Pairwise comparisons between the three graphs showed all were clinically equivalent (95% CIs between -1.0 and 1.0). In both trials, bar graph was the most preferred presentation (chosen by 32.9% of trial A participants and 35.6% in trial B).

Discussion Potential limitations included that scenarios were hypothetical, and not all participants had experience with the conditions.

Conclusion Any of the four visual presentations tested may be suitable to use when discussing quantitative prognostic information.