How Does the New Australian EQ-5D-5L Value Set Impact Utility Scores? Analysis of Data from the Australian Orthopaedic Association National Joint Replacement Registry.

Background: With advances in health state valuation methods, new value sets may be developed for some countries. Quantifying the impact of moving between existing and new value sets is critical for guiding decisions around utility score interpretation, reporting and comparison with published scores.

Objectives: The aim of this study is to examine, using large-scale national registry data, how the new Australian EQ-5D-5L value set impacts utility scores for patients undergoing joint replacement.

Methods: Data from the Australian Orthopaedic Association National Joint Replacement Registry were used for this analysis. All primary total hip (THR), knee (TKR), and shoulder replacement (TSR) procedures between 2018 and 2022 with pre-operative and 6-month post-operative EQ-5D-5L data were included. Utility scores were generated using the 2013 and 2023 Australian value sets ('previous' and 'new' value sets, respectively) and analysed descriptively for each joint replacement cohort. Agreement between the two utility score sets was evaluated using concordance correlation coefficients and Bland-Altman plots.

Results: EQ-5D-5L data were available for 17,576 THR, 23,010 TKR, and 1667 TSR procedures. The new value set produced a lowest possible EQ-5D-5L utility score of -0.30 (compared with -0.68 previously) and fewer patients had 'worse-than-dead' quality of life (score < 0.00) before surgery. Mean pre-operative scores were 0.21 (THR), 0.19 (TKR), and 0.17 (TSR) units higher with the new value set, and mean post-operative scores were 0.11-0.14 units higher. The new value set resulted in smaller effect sizes for the THR (1.08 versus 1.23) and TKR cohorts (0.86 versus 0.92). There was moderate-to-good overall agreement (coefficients: 0.70-0.80), but concordance varied by time point.

Conclusion: Although acceptable agreement was evident, the new Australian value set produces less extreme negative utility scores and markedly higher group-level scores. Transition to reporting new EQ-5D-5L utility scores will require accompanying explanation to signal measurement modifications rather than better quality of life.