Calculation of utility score
| How to calculate a utility score: an example |
| Age of the respondent 50 years |
| Age the subject expects to live 70 years |
| Response to the time-trade off question above 10 years |
| Step 1: Determine the number of additional years the patient expects to live |
| 70–50 = 20 additional years |
| Step 2: Divide the number of years the respondent is willing to give up to spend the rest of his/her living years free of glaucoma from the value obtained in step 1 |
| 10/20 = 0.50 |
| Step 3: Subtract the value obtained in step 2 from 1.0 |
| 1.0–0.50 = 0.50 |
| Interpretation: The respondent is willing to give up 50% of his/her remaining life years in a trade off for life without glaucoma. The utility value is calculated by subtracting the percentage of remaining years traded (0.50—ie, 50%) from the state of perfect health 1.0 (100%). |