Utilities are numerical expressions of patient preferences for a particular state of health.
More commonly, utilities are elicited by asking patients to make a series of choices to identify at what point they are indifferent about the choice between two options. There are two commonly used iterative approaches to assessing utilities. With the time trade-off method, for example, patients might be asked whether they would prefer to live 10 years in good health or 20 years with a disabling stroke. If they chose the latter, the choice might be modified to 15 years in good health or 20 years living with a disabling stroke. With the standard gamble method, a patient is instead asked to choose between life with a specific condition and a gamble with variable probabilities of life without the condition and death.