Prioritizing Rare Diseases: Psychological Effects Influencing Medical Decision Making

Measuring societal preferences for rarity has been proposed to determine whether paying premium prices for orphan drugs is acceptable.

To investigate societal preferences for rarity and how psychological factors affect such preferences.

A postal survey containing resource allocation dilemmas involving patients with a rare disease and patients with a common disease, equal in severity, was sent out to a randomly selected sample of the population in Sweden (return rate 42.3%, n = 1270).

Overall, we found no evidence of a general preference for prioritizing treatment of patients with rare disease patients over those with common diseases. When treatment costs were equal, most respondents (42.7%) were indifferent between the choice options. Preferences for prioritizing patients with common diseases over those with rare diseases were more frequently displayed (33.3% v. 23.9%). This tendency was, as expected, amplified when the rare disease was costlier to treat. The share of respondents choosing to treat patients with rare diseases increased when presenting the patients in need of treatment in relative rather than absolute terms (proportion dominance). Surprisingly, identifiability did not increase preferences for rarity. Instead, identifying the patient with a rare disease made respondents more willing to prioritize the patients with common diseases. Respondents' levels of education were significantly associated with choice-the lower the level of education, the more likely they were to choose the rare option.

We find no support for the existence of a general preference for rarity when setting health care priorities. Psychological effects, especially proportion dominance, are likely to play an important role when preferences for rarity are expressed.