Elicitation of utility scores in Canada for immune thrombocytopenia treated with romiplostim or watch and rescue

OBJECTIVES: The objective of this study was to obtain utilities, or preference-based quality-of-life values, from the Canadian general public, for potential health states experienced by immune thrombocytopenia (ITP) patients receiving either romiplostim (a new thrombopoietin mimetic agent) or 'watch and rescue' therapy. Utilities are needed to conduct a cost-utility analysis of romiplostim for formulary and reimbursement decisions. METHODS: An electronic Time Trade-off (TTO) survey was developed and administered to a sample of the general public in Canada, with 12 distinct health states derived from two randomized clinical trials of romiplostim vs watch and rescue treatment. Two pilot tests assessed interpretability and respondent burden. In the final survey, each subject was administered the TTO for four randomly-selected health states. Descriptive statistics were computed for utility scores, and differences between health states were evaluated with an analysis of variance model. RESULTS: Eight hundred and twenty-one adults completed the TTO survey. Mean age was 36.4 (SD = 15) years; 63% were female. Mean (SD) utility scores ranged from 0.476 (0.271) for the most severe health state (significant bleeding) to 0.633 (0.282) for the least severe health state depicting successful treatment with romiplostim. Statistical significance was found on the mean difference between the most severe health state and five other health states (p < 0.05). After adjusting utilities for matching Canadian demographic parameters, no substantial difference was found between original utility scores and adjusted scores. CONCLUSIONS: This study provides evidence of the Canadian general public's preference for 12 ITP health states pertaining to romiplostim treatment or watch and rescue. This study had a number of limitations, the main ones being the lack of perfect match in demographics between this sample and the Canadian population, as well as the fact that the scenario descriptions were based on both published literature and expert opinion. Despite those limitations, the obtained utility scores may be used in cost-utility models of romiplostim as a treatment for ITP patients in Canada.