Objectives: The aim of this study was to compare the performance of the EQ-5D-Y-3L (Y-3L) and the expanded five level version, the EQ-5D-Y-5L (Y-5L). Methods: Children/adolescents with an acute or chronic health condition and from the general population completed the Y-5L and Y-3L self-report questionnaires. Performance of the Y-5L and Y-3L was determined by comparing feasibility, redistribution of dimension responses, discriminatory power, validity, and test-retest reliability. Results. Five hundred and fifty children/adolescents completed baseline measures and 173 completed repeat measures. The ceiling effect decreased by 15% from the Y-3L to Y-5L. Informativity of dimensions improved by 0.094 on the Y-5L. There was a range of 4-9% inconsistent responses moving from the Y-3L to Y-5L. Convergent validity of the Visual Analogue Scale (VAS) and Y-3L, Y-5L dimensions was similar, weak to moderate (rs range: 0.18 – 0.38) but similar and strong on paired Y-3L and Y-5L dimensions: Kendall Tau B (range 0.69 – 0.80) and Gamma (range 0.92 – 0.98). The Y-5L and Y-3L showed moderate to substantial agreement for test-retest reliability across dimensions and VAS scores in stable chronic health conditions and fair agreement for the general population. Conclusion: The EQ-5D-Y-5L is a valid, reliable extension of the Y-3L for children/adolescents across health conditions and healthy children/adolescents. The expanded levels reduced the ceiling effect. The relative informativity of report across dimensions increased on the Y-5L compared to the Y-3L with retention of the evenness of reporting. The convergent validity and test-retest reliability of the Y-5L was comparable to the Y-3L.
