Validity and feasibility of the use of condition-specific outcome measures in economic evaluation

Background: Usually, generic questionnaires such as the EQ-5D or Health Utility Index (HUI) are used to obtain utility scores for computing QALYs. Sometimes, however, application of these instruments is not possible, or the responsiveness is doubted. An alternative strategy is to attribute utility scores to health states of a condition-specific outcomes measure (CSOM). We explored the validity and feasibility of this strategy. Research design: Our samples determined utility scores for the health states of the International Index of Erectile Function (IIEF) using time tradeoff (TTO). To reduce costs and time, the general population (n = 169) was interviewed in groups. We tested the validity of the group sessions in students. To test the extent of agreement between values obtained using the group and those obtained through individual administration, 63 students were interviewed individually and 54 in groups. Results: The utility scores for the disease-specific health states showed good construct validity. Also, the criterion validity of the adapted TTO was confirmed. Discussion: Disease-specific utility scores can be used in QALY analysis by converting them to a generic scale. Efforts should be undertaken to prevent response spreading. Administrating TTO in groups could reduce the time and costs of TTO administration and render the strategy of determining utilities for condition-specific health states more feasible.

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