Comparative Analysis of Published Italian Utility Equations: An Analysis on Simulated EQ-5D Data

OBJECTIVES: In Italy, two different equations are used to obtain utility values for each EuroQol-5D (EQ-5D) health state with country-specific tariffs, Scalone et al. (2013) for the three-level (3L) version of the questionnaire and Finch et al. (2022) for the five-level (5L) version. This analysis assesses the differences in the applications of these equations, using simulated sets of EQ-5D values.

METHODS: A synthetic cohort of 10,000 individuals was generated using Stata/MP©. Each individual was assigned 3L values according to uniform distribution across all five dimensions, to cover all 243 possible combinations of EQ-5D-3L values. Then, 3L values were mapped into 5L values using two different methodologies: one set was obtained using the mapping function developed by Van Hault and Shaw (Van Hault set), the other was obtained by converting all 2-values from the 3L states into 3-values of the 5L states, and 3L 3-values into 5L 5-values to obtain, for example, the 5L state “15531” from the 3L state “13321” (corresponding values set). The three resulting sets of EQ-5D values were then transformed into utilities through the respective equations, descriptive statistics were conducted, and results compared.

RESULTS: The Scalone equation yielded an average utility of 0.436 (Standard Deviation [SD]: 0.289), while the Finch equation resulted in lower averages of 0.359 (SD: 0.295) for the Van Hault set and 0.353 (SD: 0.305) for the corresponding values set. Consistently, the percentage of health states worse than death was 8.49% for the 3L set, 11.58% for the Van Hault set, and 13.05% for the latter set. The Finch equation provided higher values for better health states, but lower values for middle and worse health states.

CONCLUSIONS: This study shows that in a simulated setting, the equation based on Italian-specific tariffs for EQ-5D-3L values provides higher average utilities than the equation for EQ-5D-5L values.