Comprehension of confidence intervals in audio-visual patient information materials for people with multiple...

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

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.

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).

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

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