Development and initial validation of a new preference-based disease-specific health-related quality of life instrument for erectile function
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- Torrance, G., Keresteci, M., Casey, R. et al. Qual Life Res (2004) 13: 349. doi:10.1023/B:QURE.0000018482.71580.f2
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Health-related quality of life instruments may be generic or specific. In general, only generic instruments use preference-based scoring. We report on a novel approach to combine in one instrument the strengths of the specific approach, greater disease relevance and responsiveness, with those of preference-based scoring, generalizability through utilities. Objectives: The primary objective was to develop a self-administered, preference-based instrument capable of measuring utilities in the disease-specific context of erectile dysfunction (ED). Methods: Content derivation/validation began with a literature review. Eight attributes (domains) were selected to provide clinical experts structure for focus group discussion. Four levels describing a continuum of dysfunction–function were defined for each domain. Each domain, including functional levels, was reviewed and modified until consensus was achieved regarding content. This content was then integrated into a preference based scoring instrument using two visual analogue scales (VAS) with which patients rated three ‘marker’ health states (representing mild, moderate and severe ED), their self-state and a previously validated external marker state. The instrument was pilot tested, and implemented in a clinical trial. Initial validation analyses have been performed. Results: A self-administered, preference-based, VAS instrument was developed for use in the ED population, and the instrument was feasible to complete, was reliable beyond the threshold of acceptability established a priori and demonstrated good validity. Evidence of these properties accumulates over time and this study begins that process with this instrument. Responsiveness is being assessed in the context of a clinical trial.