II. Definition
- Application of Expected Utility Theory (in which decision choices are assigned an amount of satisfaction)
- Quantifies disease burden
- Application of Time Trade Off (TTO)
- State of current illness for T1 time versus Perfect health for T2 time
- How many years of perfect health (T2) are worth the same as living 10 years (T1) in your current state of health?
- TTO or Utility Value = (Perfect Health Years)/10 years = decimal number between 0 and 1
- Allows comparison when determining value of medical interventions
- TTO of 1 is perfect health
- TTO of 0 is death
- In some cases of severe, painful illness, T2 years of perfect health may be a negative number
III. Example
- Patient assigns a Time Trade Off of 3 years of perfect health equivalent to 10 years with their current illness (0.3)
- QALY = (years in current state) x TTO
- One QALY of perfect health is 1
- Patient is given a prognosis of 3 year survival in the current state of health without treatment
- QALY = TTO x 3 years = 0.3 x 3 = 0.9 years
IV. Resources
- Quality Adjusted Life Year (Wikipedia)
V. References
- Desai (2014) Clinical Decision Making, AMIA’s CIBRC Online Course