#### II. Definition

1. Application of Expected Utility Theory (in which decision choices are assigned an amount of satisfaction)
1. Quantifies disease burden
2. Application of Time Trade Off (TTO)
1. State of current illness for T1 time versus Perfect health for T2 time
2. How many years of perfect health (T2) are worth the same as living 10 years (T1) in your current state of health?
3. TTO or Utility Value = (Perfect Health Years)/10 years = decimal number between 0 and 1
3. Allows comparison when determining value of medical interventions
1. TTO of 1 is perfect health
2. TTO of 0 is death
3. In some cases of severe, painful illness, T2 years of perfect health may be a negative number

#### III. Example

1. Patient assigns a Time Trade Off of 3 years of perfect health equivalent to 10 years with their current illness (0.3)
2. QALY = (years in current state) x TTO
1. One QALY of perfect health is 1
2. Patient is given a prognosis of 3 year survival in the current state of health without treatment
3. QALY = TTO x 3 years = 0.3 x 3 = 0.9 years

#### IV. Resources

1. Quality Adjusted Life Year (Wikipedia)

#### V. References

1. Desai (2014) Clinical Decision Making, AMIA’s CIBRC Online Course