In the context of the choice of treatment for end-stage renal disease, three approaches to utility assessment were examined to determine which captures prospective patients' values best. The standard gamble (SG), time tradeoff (TTO) and visual analogue scale (VAS) were compared for their test-retest reliability and convergent validity. The study population consisted of patients who attended nephrology clinics at one of three teaching hospitals in the city of Montreal. Sixty-six patients were interviewed three times by one of two interviewers. They were taught about the treatments using an information package developed expressly for the study and a video produced by a pharmaceutical company for use in this decision context. Utilities for treatment were measured on two occasions about one week apart. / Patients differed widely in the utilities provided (responses ranged from 0 to 100) but mean utilities were similar across the treatments assessed. Because of the wide variation among subjects, the intraclass correlation coefficients for test-retest reliability were high to moderate: 0.87 for SG, 0.73 for TTO and 0.64 for VAS. However, the precision of the methods, as measured by the standard deviation of the measure from one occasion to the next within subjects, was low with SD's of 10 for SG, 14 for TTO and 13 for VAS assessments. The use of correlation coefficients as a measure of reliability and convergence in this context was challenged. / SG and TTO utilities and SG and VAS utilities (when anchoring effects were controlled) were unbiased estimates of one another, but the degree of agreement between each pair was low. The VAS assessments produced higher values than the TTO assessments. Both SG and VAS were susceptible to strong anchoring effects; in other words, the utilities obtained were different when the best and worst outcomes used to anchor the ends of the scale were changed from full health and death to full health and the worst treatment. / Subject characteristics and study factors were investigated for associations with reliability and with convergence and with the absolute level of utility. The standard gamble approach was strongly associated with many of the factors, while the time trade-off and the visual analogue utilities were associated with fewer. / The poor reliability of the methods raises questions about their use in decision aids for individuals. The lack of agreement among the methods indicates that the methods cannot be used interchangeably.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28766 |
| Date | January 1994 |
| Creators | Groome, Patti A. |
| Contributors | Hutchinson, Tom A. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Epidemiology and Biostatistics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001441252, proquestno: NN05715, Theses scanned by UMI/ProQuest. |
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