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

Abstract

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 ≥50 × 10⁹/L, no outpatient bleed: 0.863 ± 0.15; HS2: platelets ≥50 × 10⁹/L, outpatient bleed: 0.734 ± 0.19; HS3: platelets <50 × 10⁹/L, no outpatient bleed: 0.841 ± 0.19; HS4: platelets <50 × 10⁹/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.

Key words:

• Health states
• Immune (idiopathic) thrombocytopenic purpura
• Quality of life
• Utility values

Transparency

Declaration of funding

This research was funded by Amgen Inc, Thousand Oaks, CA, USA through a contract to Covance Inc.

Declaration of financial/other relationships

A.S. and C.S. have disclosed that they are employees of Covance Inc., a health outcomes research consultancy, and that they have served as paid consultants to Amgen for this research. J.B. has disclosed that he is Professor of Health Economics at the University of Sheffield and a paid advisor to Amgen. P.V. has disclosed that he is Consultant and Reader in Haematology at Weatherall Institute of Molecular Medicine, Oxford, UK and a paid advisor to Amgen. Both co-authors received honoraria from Amgen for their participation in this research. R.D. and J.I. have disclosed that they are employed by Amgen and own stock in the company.

Some peer reviewers receive honoraria from CMRO for their review work. The peer reviewers of this paper have disclosed that they have no relevant financial relationships.

Acknowledgment

The authors acknowledge the contributions of Samuel Colman for statistical support, Stephanie Cooper and Mandy Bates for support in conducting the primary research, and Susan D Mathias for her review and input on earlier versions of the manuscript.

The analyses were conducted by Covance Inc. The manuscript was subject to Amgen review prior to submission. However, A.S. maintained final control over content.