Psychometric properties of EQ-5D-5L for use in patients with Graves’ disease

Background The EQ-5D-5 L is a commonly used generic measure of health. This study aimed to evaluate the psychometric properties of the EQ-5D-5 L in patients with Graves’ disease (GD). Methods A prospective cohort of patients with GD recruited at three public hospitals in Hong Kong completed the EQ-5D-5 L and ThyPRO-39 questionnaires at baseline, 1-month, and 6-month follow-ups. Convergent validity was tested by examining the Spearman correlation between EQ-5D-5 L and ThyPRO-39 scores at baseline. 1-month test-retest reliability was assessed by Intraclass Correlation Coefficient (ICC), Gwet’s Agreement Coefficient 2 (AC2), and percentage agreement. Responsiveness of EQ-5D-5 L index and EQ-VAS scores was assessed using effect size statistics (standardized effect size [SES] and standardized response mean [SRM]). Results Of 125 recruited patients, 101 (80.8%) and 100 (80.0%) patients were followed up at 1- and 6-month, respectively. For convergent validity, there was a moderate negative correlation between EQ-5D-5 L index or EQ-VAS score and ThyPRO-39 overall QoL-impact score (-0.350, -0.451), between EQ-VAS score and composite score (-0.483), and strong negative correlation between EQ-5D-5 L index score and composite score (-0.567). The Gwet’s AC2 and percentage agreement were the highest in self-care (0.964 and 0.967), followed by mobility (0.952 and 0.962), usual activities (0.934 and 0.948), pain/discomfort (0.801 and 0.887), and anxiety/depression (0.788 and 0.882). The ICC for the EQ-5D-5 L index and the EQ-VAS was 0.707 and 0.700. For patients who reported having ‘worsened’ health at 6-month follow-up, the SES and SRM were − 0.66 and − 0.42 for EQ-5D-5 L index and − 1.15 and − 1.00 for EQ-VAS, respectively. Conclusions The EQ-5D-5 L demonstrated convergent validity, test-retest reliability, and responsiveness to worsened health status among patients with GD.