Concurrent Validity Between EQ-5D and HRQ-6D Measures in Patients with Different Primary Diagnoses

<b>Background/Objectives:</b> The HRQ-6D is a newly developed instrument to measure Health-related quality of life (HRQOL) and EQ-5D is the gold standard for measuring HRQOL. This study aims to test the concurrent validity between EQ-5D and HRQ-6D measures among patients with different primary diagnoses. <b>Methods</b>: This cross-sectional study uses two HRQOL measurement instruments, EQ-5D-3L and HRQ-6D. Data collection was performed between January 2023 and May 2023. All the necessary data for this study were collected from actual patients who presented with any one of the four different types of primary diagnoses: heart disease, cancer, depressive disorders, and end-stage renal disease (ESRD). They were recruited from the four specialist clinics that cater to the treatment of each of the four different types of primary diagnoses in a tertiary hospital. <b>Results</b>: There were 149 patients who participated in the study wherein 40 (26.8%) of them were ESRD patients, 39 (26.2%) of them were cancer patients, 38 (25.5%) of them were mentally depressed, and the remaining were patients with heart diseases. The domains in HRQ-6D, except for the perception of future health, are significantly associated with domains in EQ-5D-3L after having controlled for patients' primary diagnoses (i.e., <i>p</i> < 0.001). The HRQ-6D replaces the domain "Usual activities" with "Physical energy," and the association between these two domains is significant (<i>p</i> < 0.001). The correlation between the overall HRQ-6D and EQ-VAS scores is also significant (coefficient = 0.445, <i>p</i> < 0.001). <b>Conclusions</b>: The HRQ-6D is demonstrated to have concurrent validity with EQ-5D. Therefore, clinicians and researchers can use HRQ-6D to measure patient outcomes for interventional and observational studies. (Total word count = 265 words).