Open Access

ARTICLE

The Erectile Function Visual Analog Scale (EF-VAS): a disease-specific utility instrument for the assessment of erectile function

R. Casey¹, J. E. Tarride², M. A. Keresteci³, G. W. Torrance^2,4

1 Male Health Centre, Oakville, Ontario, Canada
2 McMaster University, Hamilton, Ontario, Canada
3 Nexus Research Solutions, Thornhill, Ontario, Canada
4 Innovus Research Inc., Burlington, Ontario, Canada
Address correspondence to M. Keresteci, Nexus Research Solutions, 24 Almond Avenue, Thornhill, Ontario L3T 1L1 Canada

Canadian Journal of Urology 2006, 13(2), 3016-3025.

Abstract

This article presents the responsiveness results of the Erectile Function Visual Analog Scale (EF-VAS) and reports, for the first time, utilities associated with erectile dysfunction (ED), as calculated by a disease-specific utility assessment. The EF-VAS is a new quality of life (QoL) instrument specific to ED that combines the strengths of the disease-specific approach to measuring QoL (greater disease relevance and responsiveness, with relevance to clinicians and patients) with those of preference-based assessments (generalizability and relevance to decision makers). The EF-VAS has demonstrated feasibility, reliability, and validity as reported in a recent publication.
Methods: Standard instrument development methodology was utilized and the finalized content was integrated into a preference-based scoring instrument comprised of two visual analogue scales (VAS). The EF-VAS was implemented in a clinical trial and data from the trial was subjected to validation analysis. Three methods were used to evaluate the responsiveness of the EF-VAS: Spearman correlations, effect size and standardized response means. VAS scores were converted to von Neumann-Morgenstern (vNM) utilities through a conversion curve.
Results: The EF-VAS was established to be responsive to changes in disease state within and between patients with ED. The EF-VAS allowed the calculation of vNM utility values and a significant increase in utility was observed in the sildenafil group compared to placebo at study end.
Conclusion: The EF-VAS represents an important advance in the understanding of the impact of ED on patients' QoL and in providing a mechanism to allow the quantification of the health status that patients associate with ED. Based on its responsiveness, the EF-VAS will provide an important clinical tool to assess and contribute to the understanding of the impact of treatment for ED. The EF-VAS represents a major advance in the science of health-related quality of life (HRQoL) assessment, as it is the first validated ED-specific utility assessment reported in the literature.

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