Overview
In economic evaluation of healthcare interventions, utilities are used to represent the strength of individuals' preferences for different health states. When utility values are averaged over a population of responders they can be considered to be valuations of health states. Conventionally, the valuations fall on a scale where 1 represents the valuation of a state of perfect health and 0 represents the valuation of death. Sequences of utility values reported over periods of time for individual patients or cohorts of patients may be aggregated to derive quality-adjusted life years, commonly used as outcomes in economic evaluation. Alternately, health states can be valued by the general population.
There are three main methods of valuing health states in the general population. Sometimes these methods are used in conjunction with each other.
1. Time trade-off.
2. Standard gamble.
3. The visual analogue scale.
Descriptions and demonstrations of each of these methods can be found on each tab.
Time Trade-Off
Time trade-off (TTO) is a choice-based method of eliciting health state utility, which reflects the length of remaining life expectancy that a person may be prepared to trade-off in order to avoid remaining in a sub-perfect health state. A demonstration of this method can be played out below:
1. Pick a random health state.
2. Consider the two options in the purple boxes. Pick the option you would prefer, and then the number of years will adjust to narrow-in on the exact length of time you would trade off.
3. If you reach a point where you value both options the same, select the 'I am indifferent' box.
4. Otherwise, the calculator will narrow down to a single utility value for you.
Standard Gamble
Standard gamble (SG) is a choice-based method of eliciting health state utility, which reflects the chance that someone is willing to gamble on in order to avoid remaining in a sub-perfect health state. A demonstration of this method can be played out below:
1. Pick a random health state.
2. Consider the two options in the purple boxes. Pick the option you would prefer, and then the probability will adjust to narrow-in on the exact risk you would be willing to take.
3. If you reach a point where you value both options the same, select the 'I am indifferent' box.
4. Otherwise, the calculator will narrow down to a single utility value for you.
Visual Analogue Scale
The visual analogue scale is a method of eliciting health state utility which asks people to rate their health on a 0-100 scale. A demonstration of this method can be played out below:
1. Pick a random health state.
2. Imagine you permanently experienced the health state and consider what you would rate your health out of 100.
3. Select and confirm that value on the slider, and this is your valued utility for that state.