Psychometric Properties of EQ-5D-3L Applied through Phone Follow-Ups: An Experience in PERSIAN Traffic Cohort.

Objective: To assess psychometric properties of the European Quality of Life 5-Dimension 3-Level Version (EQ-5D-3L) commonly used tool for measuring road traffic injury (RTI) patients' quality of life.

Methods: The psychometric study assessed the reliability and applicability of EQ-5D-3L through phone surveys, based on a national cohort platform. Data of 150 RTI patients recruited from the cohort study were included as 50 patients per each follow-up phase (one, six, and twelve months after discharge). A 12- day-time span was between test and retest. We measured psychometric properties (internal consistency reliability and stability reliability) and agreement using Kappa coefficients and percentages of agreement and Bland-Altman method. Data were analysed using software STATA statistical package.

Results: The majority of patients were men (80%) with mean age (SD) of 41(14.7%), employed (78%) and educated (86%). The Persian version represented high internal consistency reliability at total level (Cronbach's α=0.81) and moderate to good reliability at phase levels (0.62-0.87). The stability reliability was excellent at total (ICC=0.98, 95% CI: 0.97, 0.98) and phase levels (0.97-0.98. The kappa agreement coefficients were valued moderate to perfect (0.6-0.8, p>0.0001). The Bland-altman plot illustrated high agreement between test and retest scores. No floor and ceiling effects were found.

Conclusion: The study revealed that EQ-5D-3L was highly reliable and responsive to be applied through phone interviews at three different times post injury and discharge, as no previous study considered its psychometric properties at various phone follow-ups after RTIs.