A head-to-head comparison of EQ-5D-5L and SF-6D in Dutch patients with fractures visiting a Fracture Liaison Service

This study compared the psychometric properties of EQ-5D-5L and SF-6D to assess the interchangeability of both instruments in patients with a recent fracture presenting at a Fracture Liaison Service (FLS). Data from a prospective observational study in a Dutch FLS clinic were used. Over three years, subjects were interviewed at several time points using EQ-5D-5L and SF-36. Floor and ceiling effects were evaluated. Agreement was evaluated by intra-class correlation coefficients and visualized in Bland-Altman plots. Spearman's rank correlation coefficients were applied to assess convergent validity. Mann-Whitney U test or Kruskal-Wallis H test as well as effect size (ES) were used to explore known-groups validity. Responsiveness was explored using standardized response mean (SRM) and ES. For each measurement property, hypotheses on direction and magnitude of effects were formulated. A total of 499 patients were included. EQ-5D-5L had considerable ceiling effect in comparison to SF-6D (21% vs. 1.2%). Moderate agreement between the (UK and Dutch) EQ-5D-5L and SF-6D was identified with intra-class correlation coefficients of 0.625 and 0.654, respectively. Bland-Altman plots revealed proportional bias as the differences in utilities between two instruments were highly dependent on the health states. High correlation between instruments was found (UK: rho =0.758; Dutch: rho =0.763). EQ-5D-5L and SF-6D utilities showed high correlation with physical component score but low correlation with mental component score of SF-36. Both instruments showed moderate discrimination (ES >0.5) for subgroup by baseline fracture type, and moderate responsiveness (SRM >0.5) in patients that sustained a subsequent fracture. Both EQ-5D-5L and SF-6D appeared to be valid utility instruments in patients with fractures attending the FLS. However, they cannot be used interchangeably given only moderate agreement was identified, and differences in utilities and ceiling effect were revealed. Comparable construct validity and responsiveness were indicated, and neither instrument was found to be clearly superior.