Purpose. Many analyses of medical treatments entail the aggregation of health outcomes over patients and over time. This study assessed the extent to which voters, medical administrators, and physicians consider such aggregation to be appropriate. In addition, the study assessed whether this perceived fungibility of outcomes moderates the difference between treatment recommendations in single-play decisions (for 1 patient on 1 occasion) and those in repeated-play decisions (for several patients or for 1 patient on several occasions). Methods. In a 5-contact mail survey of registered voters (n = 182, response rate = 52%), medical administrators (n = 123, 35%), and physicians (n = 95, 26%), respondents rated the fungibility of outcomes and indicated their preferred action in 1 of 3 scenarios involving changes in life expectancy or the duration of pain. They evaluated a risky, positive-expected-value treatment in a single-play decision, then in a repeated-play decision, and again in a repeated-play decision after they viewed the distribution of possible net outcomes. Results. Perceived fungibility varied substantially across respondents in all groups, with voters giving higher fungibility ratings than administrators or physicians. Respondents’ strength-of-preference ratings for treatment increased from single-play to repeated-play decisions, but these increases were moderated by perceived fungibility, as expected. When outcomes were considered fungible, treatments were much more attractive in repeated-play decisions than in single-play decisions. When outcomes were considered nonfungible, there was essentially no difference between single- and repeated-play decisions. Conclusions. Recommendations regarding risky medical treatments with positive expectations appear to depend, in part, on opinions about whether it is reasonable to aggregate medical outcomes over patients or over time. Such opinions vary widely among physicians and others.
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