From clinically relevant outcome measures to quality of life in epilepsy: A time trade-off study

• Development of population based utilities with the time trade off method.
• Clinically relevant epilepsy outcome measures are transformed into utility estimates.
• Appropriate utility estimations for economic evaluations based on clinical outcomes.
• Seizure severity is the most important factor on utility.

ObjectivesA proposed method for bridging the gap between clinically relevant epilepsy outcome measures and quality-adjusted life years is to derive utility scores for epilepsy health states. The aim of this study is to develop such a utility-function and to investigate the impact of the epilepsy outcome measures on utility.MethodsHealth states, based on clinically important epilepsy attributes (e.g. seizure frequency, seizure severity, side-effects), were valued by a sample of the Dutch population (N = 525) based on the time trade-off method. In addition to standard demographics, every participant was asked to rate 10 or 11 different health state scenarios. A multilevel regression analysis was performed to account for the nested structure of the data.ResultsResults show that the best health state (no seizures and no side-effects) is estimated at 0.89 and the worst state (seizures type 5 twice a day plus severe side-effects) at 0.22 (scale: 0–1). An increase in seizure frequency, occurrence of side-effects, and seizure severity were all significantly associated with lower utility values. Furthermore, seizure severity has the largest impact on quality of life compared with seizure frequency and side-effects.ConclusionsThis study provides a utility-function for transforming clinically relevant epilepsy outcome measures into utility estimates. We advise using our utility-function in economic evaluations, when quality of life is not directly measured in a study and hence, no health state utilities are available, or when there is convincing empirical evidence of the insensitivity of a generic quality-of-life-instrument within epilepsy.