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

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. The psychometric study assessed the reliability and applicability of EQ-5D-3L through phonesurveys, based on a national cohort platform. Data of 150 RTI patients recruited from the cohort study wereincluded as 50 patients per each follow-up phase (one, six, and twelve months after discharge). A 12- day-timespan was between test and retest. We measured psychometric properties (internal consistency reliability andstability reliability) and agreement using Kappa coefficients and percentages of agreement and Bland-Altmanmethod. Data were analysed using software STATA statistical package. The majority of patients were men (80%) with mean age (SD) of 41(14.7%), employed (78%) andeducated (86%). The Persian version represented high internal consistency reliability at total level (Cronbach’sα=0.81) and moderate to good reliability at phase levels (0.62-0.87). The stability reliability was excellent attotal (ICC=0.98, 95% CI: 0.97, 0.98) and phase levels (0.97-0.98. The kappa agreement coefficients were valuedmoderate to perfect (0.6-0.8, p>0.0001). The Bland-altman plot illustrated high agreement between test andretest scores. No floor and ceiling effects were found. The study revealed that EQ-5D-3L was highly reliable and responsive to be applied through phoneinterviews at three different times post injury and discharge, as no previous study considered its psychometricproperties at various phone follow-ups after RTIs.