Medical Decision Making (MDM)
November 2015; 35 (8)
http://mdm.sagepub.com/content/current

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Presenting Numeric Information with Percentages and Descriptive Risk Labels
A Randomized Trial
Aleksandr Sinayev, MA, Ellen Peters, PhD, Martin Tusler, MA, Liana Fraenkel, MD, MPH
Ohio State University, Columbus, OH (AS, EP, MT)
Yale School of Medicine, New Haven, CT (LF)
Abstract
Background.
Previous research demonstrated that providing (v. not providing) numeric information about the adverse effects (AEs) of medications increased comprehension and willingness to use medication but left open the question about which numeric format is best. The objective was to determine which of 4 tested formats (percentage, frequency, percentage + risk label, frequency + risk label) maximizes comprehension and willingness to use medication across age and numeracy levels.
Methods.
In a cross-sectional internet survey (N = 368; American Life Panel, 15 May 2008 to 18 June 2008), respondents were presented with a hypothetical prescription medication for high cholesterol. AE likelihoods were described using 1 of 4 tested formats. Main outcome measures were risk comprehension (ability to identify AE likelihood from a table) and willingness to use the medication (7-point scale; not likely = 0, very likely = 6).
Results.
The percentage + risk label format resulted in the highest comprehension and willingness to use the medication compared with the other 3 formats (mean comprehension in percentage + risk label format = 95% v. mean across the other 3 formats = 81%; mean willingness = 3.3 v. 2.95, respectively). Comprehension differences between percentage and frequency formats were smaller among the less numerate. Willingness to use medication depended less on age and numeracy when labels were used. Generalizability is limited by the use of a sample that was older, more educated, and better off financially than national averages.
Conclusions.
Providing numeric AE-likelihood information in a percentage format with risk labels is likely to increase risk comprehension and willingness to use a medication compared with other numeric formats.

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Preferences for Vaccination: Does Health Literacy Make a Difference?
Jorien Veldwijk, Iris van der Heide, Jany Rademakers, A. Jantine Schuit, G. Ardine de Wit,
Ellen Uiters, and Mattijs S. Lambooij
Med Decis Making November 2015 35: 948-958, first published on September 3, 2015 doi:10.1177/0272989X15597225
Abstract
Purpose.
The purpose of this study is to examine to what extent health literacy is associated with parental preferences concerning childhood vaccination.
Methods.
A cross-sectional study was conducted among 467 Dutch parents of newborns aged 6 weeks (response rate of 37%). A self-reported questionnaire was used to measure health literacy by means of Chew’s Set of Brief Screening Questions, as well as parental preferences for rotavirus vaccination by means of a discrete choice experiment. Five rotavirus-related characteristics were included (i.e., vaccine effectiveness, frequency of severe side effects, location of vaccination, protection duration, and out-of-pocket costs). Panel latent class models were conducted, and health literacy and educational level were added to the class probability model to determine the association between health literacy and study outcomes.
Results.
Lower educated and lower health literate respondents considered protection duration to be more important and vaccine effectiveness and frequency of severe side effects to be less important compared with higher educated and higher health literate respondents. While all respondents were willing to vaccinate against rotavirus when the vaccine was offered as part of the National Immunization Program, only lower educated and lower health literate parents were willing to vaccinate when the vaccine was offered on the free market.
Conclusion:
Health literacy is associated with parents’ preferences for rotavirus vaccination. Whether differences in vaccination decisions are actually due to varying preferences or might be better explained by varying levels of understanding should be further investigated. To contribute to more accurate interpretation of study results, it may be advisable that researchers measure and report health literacy when they study vaccination decision behavior.