Psychometric properties of the EQ-5D-3L in South Australia: a multi-method non-preference-based validation study.

Objective: Although HRQoL tools such as the EQ-5D-3L are significant in determining health status, these measures have not been validated in general populations in Australia. This study aims to psychometrically validate the EQ-5D-3L in a large population sample in Australia for the first time.

Methods: The EQ-5D-3L was included in the Dental Care and Oral Health study (DCOHS), conducted in a South Australian population sample. The participants were 23-91 years old, and 44.1% were male. The EQ-5D-3L was responded to on a three-point rating scale ("none"/"no", "some" and "extremely"/"unable"/"confined"). We employed the area under the receiver operating characteristic curve (AUROC) to evaluate whether the EQ-5D-3L total score could identify participants with diagnosed diseases and mental health disorders. Psychometric validation of the EQ-5D-3L investigated dimensionality with Exploratory Graph Analysis, model fit, floor/ceiling effects and criterion validity.

Results: The EQ-5D-3L comprised two dimensions, Activities and Symptoms. According to Root Mean Squared Error of Approximation (RMSEA) (<.05) and Comparative Fit Index (CFI) (>.950), the 2-dimensional structure showed excellent model fit with good reliability for the Activities subscale (Ω = 0.80-95% CI [0.77, 0.83]), and poor reliability for the Symptom subscale (Ω = 0.56-95% CI [0.53, 0.58]). The EQ-5D-3L showed adequate reliability (Ω = 0.70-95% CI [0.67, 0.72]). The EQ-5D-3L showed good discrimination for diagnosed diseases (ranging from 64.3% to 86.3%). Floor/ceiling effects were observed across all items. The EQ-5D-3L total score discriminated between respondents who were experiencing health conditions (e.g. cancer, cardiovascular disease, stroke) from healthy individuals.

Discussion: Despite the ceiling effects, the EQ-5D-3L displayed good psychometric properties as an HRQoL measure and discriminated between health states in the general South Australian population. Further research should investigate the psychometric properties of the EQ-5D-5L in South Australia and whether an increased number of response categories can mitigate the observed ceiling effects.