To illustrate how QALYs are calculated, let's consider a hypothetical patient who is being treated for a chronic condition. We'll assume that the patient is 50 years old and has a life expectancy of 30 years. We'll also assume that the patient's utility score is 0.7 (i.e., the patient's quality of life is 70% of perfect health).
Now, let's consider two different treatment options for this patient. Treatment A costs $10,000 per year and is expected to extend the patient's life by 5 years, with a utility score of 0.8. Treatment B costs $20,000 per year and is expected to extend the patient's life by 10 years, with a utility score of 0.6.
To calculate the QALYs for each treatment option, we first multiply the number of years by the utility score to get the number of QALYs for each year. For Treatment A, we get:
5 years x 0.8 utility score = 4 QALYs
For Treatment B, we get:
10 years x 0.6 utility score = 6 QALYs
Next, we add up the total number of QALYs for each treatment option and divide by the total cost to get the cost-effectiveness ratio:
Treatment A: 4 QALYs / $10,000 = 0.4 QALYs per $1,000
Treatment B: 6 QALYs / $20,000 = 0.3 QALYs per $1,000
In this example, Treatment B is more cost-effective than Treatment A, as it produces more QALYs per dollar spent. However, it's important to note that the decision about which treatment option to choose may depend on other factors, such as the patient's preferences and values, as well as the availability of alternative treatments.