baseline =
= (quality of life measure) * (number of years)
quality adjusted life years gained =
= ((quality of life measure with treatment) - (baseline quality of life measure)) * (number of years)
Factors used in the calculations:
(1) Time periods may be a fixed interval or can be for the patient's remaining life. Since a person's condition may change over time, there may be subintervals with different quality of life and greater or lesser resource utilization.
(2) The quality of life measures may range from 0.00 (worse imaginable state) to 1.00 (best possible state). In Europe the EUROQOL instrument is often used.
(3) The final quality of life measure involves both any improvements from the treatment and any adverse side effects.
(4) If the life span changes due to treatment, then the changes in cost of living and baseline care costs may need to be considered in the calculations.
cost per QALY gained =
= (net cost of treatment) / (number of QALYs gained)
where:
• The net cost of treatment includes the cost of therapy, money saved by the intervention, and the cost to manage complications.
Limitations:
• The more complex the medical condition, the more complex the calculations to compute the QALY need to be.
