Objective: The aim of this study was to evaluate the psychometric properties of the EQ-5D-5L and SF-6D, and to compare their performance among patients living with haemophilia in China.
Methods: A total of 875 Chinese patients completed the EQ-5D-5L, SF-6D, and Haem-A-QoL questionnaires. Construct validity of the EQ-5D-5L and SF-6D dimensions and indices was assessed by testing hypotheses relating these measures to Haem-A-QoL and clinical measures. The Spearman correlation coefficient was used to assess convergent validity, and one-way analysis of variance (F statistic) was used to assess the known-groups validity (discriminatory power). The agreement between EQ-5D-5L and SF-6D indices was assessed using the intraclass correlation coefficient (ICC) and the Bland-Altman plot.
Results: Both the EQ-5D-5L and SF-6D indices showed acceptable ceiling and floor effects. As hypothesised, both EQ-5D-5L and SF-6D were significantly correlated with Haem-A-QoL (both dimensions and overall score). EQ-5D-5L and SF-6D indices as well as EQ-VAS differentiated patients are known to differ in severity of haemophilia, bleeding status, disabling levels, and comorbidity. The F statistics in the known-groups comparisons suggested that the EQ-5D-5L was slightly more discriminative than the SF-6D. ICC (0.41) and Bland-Altman plot confirmed that the agreement between the EQ-5D-5L and SF-6D indices was poor.
Conclusion: Both EQ-5D-5L and SF-6D showed satisfactory construct validity in the measurement of the HRQoL among patients with haemophilia. However, the two instruments may not be used interchangeably in this patient population due to their poor agreement and differing discriminatory power.
Keywords: EQ-5D; Haemophilia; Psychometric property; Quality of life; Rare disease; SF-6D.