Measurement of utility values in the UK for health states related to immune thrombocytopenic purpura.

Objective: To measure utility values associated with immune (idiopathic) thrombocytopenic purpura (ITP), as perceived by the United Kingdom (UK) general public.
Research Design and Methods: A multi-step process, including clinical trial data, literature review, and patient focus group, was used to develop ITP health states valued in a web survey. Six ITP health states were defined based on platelet levels, risk of bleeding and key adverse events/disease complications. Clinical trial data on bleeding and ITP-specific quality of life data were key sources for developing health-state descriptions. 359 respondents, randomly selected from a managed web panel in the UK, completed the web-based Time Trade-Off survey. Wilcoxon signed-rank test was used to compare differences between each pair of health states.
Results: Sample characteristics (mean age: 47.9 +/- 16.9 years; 54% female) were comparable to the UK general population. ITP health states were valued as significantly worse than perfect health. Experiencing bleeding episodes was a more important driver than low platelet levels in valuing a health state to be worse. Substantial disutilities were associated with surviving an intracranial haemorrhage. Mean (SD) utility values for each ITP health state are: HS1: platelets >or=50 x 10(9)/L, no outpatient bleed: 0.863 +/- 0.15; HS2: platelets >or=50 x 10(9)/L, outpatient bleed: 0.734 +/- 0.19; HS3: platelets <50 x 10(9)/L, no outpatient bleed: 0.841 +/- 0.19; HS4: platelets <50 x 10(9)/L, outpatient bleed: 0.732 +/- 0.19; HS5: intracranial haemorrhage (2-6 months): 0.038 +/- 0.46; HS6: steroid treatment adverse events: 0.758 +/- 0.20. Potential limitations relate to web user population characteristics and lack of comparative testing of web-based TTO methods.
Conclusions: Results provide evidence that the UK general population associate substantial loss of value living with ITP, suggesting an important role for new ITP treatments. Utility values based on these health states may be useful in future cost-effectiveness studies of existing and/or new ITP treatments.