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Purpose: Effective communication of risk/benefit information requires the recipient to understand probabilistic information. Comprehension may be affected by whether the format in which the information is presented (i.e. using numbers or words) matches peoples’ preferences. Positive or adverse effects on comprehension would be particularly relevant when seeking informed consent for RCT participation. An experimental design was used to test whether comprehension was affected by information format “match” or “mismatch”. Methods: A convenience sample of 228 subjects, recruited from various clinical and community sites, received pre-assembled randomized packages. These packages contained: a) a sham consent form containing risk and benefit information in either numeric or verbal format; and questionnaires assessing b) the primary outcome of comprehension; and c) underlying format preference. Results: The study design identified emergent “match”(n = 105) and “mismatch” (n = 119) subgroups, based on whether or not the received format was congruent with the subjects’ reported preferences. Overall, 32.5% of subjects achieved correct responses to all 8 comprehension items, and comprehension scores did not differ between the subgroups. However, the type of match/mismatch did demonstrate an effect. Among the 46 subjects who preferred the verbal format, comprehension scores were lower, regardless of whether they received a “match” (n = 20; mean 3.80) or a “mismatch” (n = 26; mean 5.46). Among the 178 subjects who preferred the numeric format, comprehension scores did not differ significantly between those who received a “match” (n = 85, mean 6.83) and those who received a “mismatch” (n = 93, mean 6.78). Conclusions: This study is unique, in that it investigates the effects of format/preference match or mismatch on the comprehension of probabilistic information that is required for genuine consent to RCT entry. A notable proportion would not have provided a fully informed RCT consent/refusal. Those who preferred verbal format were not helped by receiving a format match and their comprehension scores were lower. Results imply that individualized assessment of format preferences and numeracy skills could point to strategies to foster adequate levels of comprehension. The study design could guide future exploratory investigations in other contexts.
See more of Oral Concurrent Session B - Methods in Judgment and Decision Making
See more of The 26th Annual Meeting of the Society for Medical Decision Making (October 17-20, 2004)