Validity of utilities of patients with esophageal cancer
Objectives: The convergent validity between utility assessment methods was assessed.
Methods: Investigated were patients with esophageal cancer treated surgically with curative intent. Patients were interviewed in a period from 3 to 12 months after surgical resection. Patients evaluated their actual health and seven other states. Visual analogue scale (VAS) and standard gamble (SG) utilities were obtained for the health states in an interview. Patients also indicated whether or not they preferred death to living in a health state (worse than dead [WTD] preferences).
Results: Fifty patients completed the interview. Convergent validity was excellent at the aggregate and individual level. However, the relation between VAS and SG differed strongly across individuals. On a scale from 0 (dead) to 100 (perfect health), SG scores were lower for patients with WTD preferences (mean difference d=35; p=.002); however, VAS scores did not vary by WTD preferences.
Conclusions: In general, there is good agreement between VAS and SG measures, although patients disagree about how the VAS and SG are related. The standard gamble varied by WTD preferences, however, the VAS did not.
Key Words: Utility assessment; Esophageal cancer.