Comparison of generic, condition-specific and mapped health state utility values

Objective: Resource allocation informed by cost-utility analysis requires that the benefits are comparable across patient groups and interventions. One option is to recommend the use of one generic utility measure, but this raises the issue of comparability when the preferred measure is inappropriate or unavailable. Many cancer trials do not include generic measures such as EQ-5D and instead include condition-specific measures and use these to generate utility estimates. We analyse the comparability of generic, condition-specific and mapped utility values for a multiple myeloma cancer patient dataset.

Methods: Generic EQ-5D, condition-specific EORTC-8D and mapped EQ-5D utility values are compared using psychometric and statistical analysis to determine discrimination across severity groups, responsiveness and agreement.

Results: Generic, condition-specific and mapped utility estimates were responsive and show discriminative validity. EQ-5D had higher responsiveness and detected a greater change across severity groups and treatment periods than EORTC-8D, but has a higher proportion of responses at full health (12.2%). Differences in EQ-5D and EORTC-8D were due to both differences in classification system and preference weights.

Conclusion: Our findings suggest that condition-specific EORTC-8D or mapped EQ-5D utility estimates are comparable to directly obtained EQ-5D utilities. EORTC-8D estimates captured problems in quality of life at the upper end of the utility scale that were not captured by EQ-5D, but estimated lower utility gains than the use of EQ-5D directly.