Measuring health state preferences for hemophilia: development of a disease-specific utility instrument

Generic and disease-specific instruments have been used to assess health-related quality of life (HRQoL) in hemophilia. However, HRQoL measures also need to reflect patient preferences for various hemophilia health states. The goal of this project was to develop a disease-specific utility instrument that measures patient preferences for various health states unique to hemophilia. The visual analog scale (VAS) and the standard gamble (SG) methods were used. Study participants (n = 128) were tested and stratified into paediatric and adult groups. Test-retest reliability was demonstrated for both instruments, with r = 0.91 for the VAS and r = 0.79 for the SG. When comparing results by age group, statistically significant differences were observed between paediatric and adult participants with the SG instrument (P = 0.045), with older participants taking more risk overall. However, no significant differences based on age were seen when using the VAS (P = 0.636). Statistically significant differences were observed between the VAS and SG instruments within both the paediatric and adult groups (P < 0.0001). In general, the SG yielded higher preference scores than the VAS for the majority of health states. Results derived from the SG instrument indicate that age can influence patients' preferences regarding their state of health. This can have implications for considering treatment options based on the mean age of the population under consideration. Both instruments demonstrated reliability and validity indicating that they could be used to assess patient preferences in hemophilia. However, preference score differences indicate that the two measures may not be interchangeable.