Estimation of an Instrument-Defined Minimally Important Difference in EQ-5D-5L Index Scores Based on Scoring Algorithms Derived Using the EQ-VT Version 2 Valuation Protocols

Objectives: To estimate and compare the minimally important difference (MID) in index score of country-specific EQ-5D-5L scoring algorithms developed using EuroQol Valuation Technology protocol version 2, including algorithms from Germany, Indonesia, Ireland, Malaysia, Poland, Portugal, Taiwan, and the United States. Methods: A simulation-based approach contingent on all single-level transitions defined by the EQ-5D-5L descriptive system was used to estimate the MID for each algorithm. Results: The resulting mean (and standard deviation) instrument-defined MID estimates were Germany, 0.083 (0.022); Indonesia, 0.093 (0.012); Ireland, 0.098 (0.023); Malaysia, 0.072 (0.010); Poland, 0.080 (0.030); Portugal, 0.080 (0.018); Taiwan, 0.101 (0.010); and the United States, 0.078 (0.014). Conclusions: These population preference-based MID estimates and accompanying evidence of how such values vary as a function of baseline index score can be used to aid interpretation of index score change. The marked consistency in the relationship between the calculated MID estimate and the range of the EQ-5D-5L index score, represented by a ratio of 1:20, might substantiate a rule of thumb allowing for MID approximation in EQ-5D-5L index score warranting further investigation.