The Influence of Varying Cost Formats on Preferences.

BACKGROUND: Numerous studies have found that cost strongly influences patients' decision making. The objective of this study was to explore the impact of varying cost formats on patients' preferences. METHODS: Mechanical Turk workers completed a choice-based conjoint (CBC) survey. The CBC survey was designed to examine stated preferences for the use of second-line agents to treat diabetes across 5 attributes: route of administration, efficacy, risk of low blood sugar, frequency of checking blood sugar levels, and cost. We developed 7 versions of the CBC survey that were identical except for the cost attribute. We described cost in terms of: Affordability, Monthly Co-pay, Dollar Sign Rating, How Expensive, or How Cheap compared with other medications, Working Hours Equivalent (per mo) and Percent of Monthly Income. The resulting part-worth utilities were used to calculate the relative importance of cost and to estimate treatment preferences for exenatide, a sulfonylurea, and insulin. RESULTS: The relative impact of cost varied significantly across the 7 formats. Cost had the greatest influence on participants' decisions when framed in terms of Affordability [mean (SD) relative importance, 37.3 (0.9)] and the lowest influence when framed in terms of How Cheap (compared with other drugs) [12.1 (0.9)]. A sulfonylurea was strongly preferred across 4 of the 7 formats. Preference for insulin, the most effective, albeit riskiest, option was low across all cost formats. CONCLUSIONS: The format used to describe cost affects how the attribute impacts patients' preferences. Individuals are most cost-sensitive when cost is framed in terms of affordability and least cost-sensitive when cost is described in terms of how cheap the medication is compared with others.