Comprehension of confidence intervals in audio-visual patient information materials for people with multiple sclerosis (COCO-MS): A web-based randomised controlled, parallel group trial

OBJECTIVES: To evaluate patient information materials on confidence intervals (CIs) in multiple sclerosis to be used with patient decision aids.

METHODS: Web-based randomised controlled parallel group trial with four study arms. Participants were equally allocated to one of three versions of audio-visual patient information or to a standard written information (arm IV). In the short version (arm III), CIs were explained without using an example, in the other two versions examples were used (arm I and arm II). The examples are based on an apple farmer who wants to estimate the average weight of his apples (arm I) and to test a treatment against worms (arm II). Primary endpoint was comprehension of CIs, assessed with a six-item multiple-choice questionnaire.

RESULTS: 855 of 1068 (80 %) randomised participants completed the survey (71 % arm I, 73 % arm II, 87 % arm III, 90 % arm IV). The median of correctly answered questions on CIs was 4 out of 6 questions in arms I and II and 5 out of 6 questions in arm III. Compared to the standard information (arm IV), all the other arms scored better on the comprehension questionnaire (ANOVA, p ≤ 0.003).

CONCLUSIONS: Information about CIs can be presented comprehensibly. High scores and a high rate of completers indicate that the short version is the favourable one.

PRACTICE IMPLICATIONS: Information materials on CIs should be used alongside absolute risk reductions in patient decision aids to enhance the interpretation of study results.