How does the EQ-5D-Y Proxy version 1 perform in 3, 4 and 5-year-old children?

The dimension of Looking after Myself is problematic for these young children but most notably so in the 3 year old group. If one considers the summary scores of the EQ-5D-Y Proxy version 1 it appears to work well. Known group validity was demonstrated. Concurrent validity was demonstrated on a composite level but not for individual dimensions of Usual Activities or Worried, Sad or Unhappy.. The observable dimensions demonstrated stability over time, with the inferred dimensions (Pain or Discomfort and Worried, Sad or Unhappy) less so, which is to be expected. Further work is needed in exploring either the adaptation of the dimensions in the younger age groups.