Assessing the preferences of patients with psoriasis. A quantitative, utility approach.

BACKGROUND AND DESIGN

Patient preferences for health outcomes can be explicitly assessed and expressed in quantitative terms known as utilities. Three standard methods for utility assessment have been used to quantify patient preferences, but these methods have not previously been applied to skin disease. Eighty-seven patients with psoriasis from a tertiary medical center were interviewed, using an interactive, computer-based utility assessment questionnaire, U-Titer. Utilities for three categories of psoriasis severity and potential adverse outcomes of methotrexate therapy were assessed by the vertical rating scale, time trade-off, and standard gamble.

RESULTS

Patients assigned a broad range of utilities for each of the health states. Utilities obtained by the vertical rating scale did not correlate well with utilities obtained by standard gamble or time trade-off methods. However, utilities assessed by standard gamble and time trade-off were not significantly different. Patient characteristics such as age, gender, and education were not correlated with utility and did not explain the variation. Indicators of the patients' disease severity were not predictive of utilities for the assessed health states. The relatively high utility for liver biopsy suggests that there is less patient aversion to the procedure than suspected.

CONCLUSIONS

Utilities, or quantitative measures of patient preferences for health states, are measurable and vary widely for mild, moderate, and severe psoriasis and possible adverse outcomes of methotrexate treatment. The process of elucidating individual patient utilities for various health outcomes can be used to incorporate patient preferences into the process of clinical decision making. Guidelines that are based solely on severity of symptoms, without input from patients on how they value such symptoms, must be questioned.