To examine the concurrent validity of the Weight-specific Adolescent Instrument for Economic evaluation (WAItE) as compared with the generic, preference-based Child Health Utility 9D (CHU-9D) and the weight-specific Youth Quality of Life—Weight (YQOL-W) and also to examine the test-retest reliability of the WAItE.
An online survey was used to administer the 3 instruments on a sample of adolescents (aged 11-18 years). Individual responses were converted into either utility scores (CHU-9D) or health-related quality-of-life scores (WAItE and YQOL-W). A 10% subsample of the respondents also completed the WAItE 1 week after completion to assess test-retest reliability.
One thousand adolescents completed the online survey. There was a strong correlation between the WAItE and both the CHU-9D (0.731; P.001). All 3 instruments were able to discriminate according to different weight status categories and a measure of self-assessed health. Unlike the CHU-9D or the YQOL-W, the WAItE did not show a substantial ceiling effect. The WAItE also showed acceptable levels of test-retest reliability.
The study results are encouraging, and illustrate that the WAItE can be used to reliably and accurately measure weight-specific outcomes in the younger population. The WAItE can also be used to assess outcomes in cost-effectiveness analysis of weight management interventions for young people, given the instrument is less likely to display ceiling effects and may thus be more sensitive in measuring change that results from interventions developed for this population.