Wijnen BFM, et al. - This study strived to examine the responsiveness of and correlation between the EQ-5D-5L and the QOLIE-31P in patients with epilepsy. Furthermore, the researchers developed a mapping function to predict EQ-5D-5L values based on the QOLIE-31P for use in economic evaluations. They emphasized the shortcomings of the EQ-5D-5L in epilepsy and the importance of the development of condition-specific preference-based instruments which could be used within the QALY framework. Moreover, in economic evaluations, the usefulness of the constructed mapping function was questionable.

• The researchers derived the dataset from 2 clinical trials, the ZMILE study in the Netherlands and the SMILE study in the UK.
• They measured patients’ quality of life using the EQ-5D-5L and QOLIE-31P at baseline and 12 months follow-up in both studies.
• They calculated Spearman’s correlations, effect sizes (EF) and standardized response means (SRM) for both the EQ-5D-5L and QOLIE-31P domains and sub scores.
• They derived mapping functions using ordinary least square (OLS) and censored least absolute deviations models.

• The researchers included 509 patients in this study.
• They found low to moderately strong significant correlations between both instruments.
• The EQ-5D-5L demonstrated high ceiling effects and small EFs and SRMs, while the QOLIE-31P did not show ceiling effects and also showed small to moderate EFs and SRMs.
• The different mapping functions suggested that the highest adjusted R² regressed was 0.265, through an OLS model with squared terms.
• It led to a mean absolute error of 0.103.