OBJECTIVES: The EQ-5D-Y-5L (Y-5L) includes the same five dimensions of health-related quality of life (HRQoL) as the adult version. The Y-5L is one of several commonly used generic measures of child HRQoL, including the Health-Utilities-Index (HUI), Child-Health-Utility (CHU9D) and PedsQL. The instruments differ in terms of what they measure. This study aims to explore the measurement relationship between the Y-5L and the other mentioned HRQoL instruments.

METHODS: All data were obtained from Australian Paediatric Multi-Instrument Comparison Study (P-MIC) [1]. The instruments were completed either by proxies or by children. Exploratory Factor Analysis (EFA) was used to investigate the underlying dimensional structure. The suitability of data for EFA was checked using Kaiser-Meyer-Olkin and Bartlett's test of sphericity. The number of factors was based on eigenvalues greater than one. This study used loadings more than 0.3. Oblique rotation (Promax) was used for this study.

RESULTS: When applying EFA to the pooled model, additional domains not included in the Y-5L can be identified. Results suggest a six-factor structure for the proxy completed surveys and a six-factor structure for the self-report. Factors related to mental health, pain and daily activities were covered by the Y-5L; however, factors related to social functioning, school functioning and senses were not.

In comparison to Y-5L, for both proxy and self-report, EFA shows that PedsQL adds an additional factor which measures social and school functioning; HUI3 adds a factor which includes items measuring senses (hearing and vision).

CONCLUSIONS: This study provides information to guide choice of generic instrument when measuring particular domains of HRQoL. The results suggest factors that may represent candidate items for Y-5L bolt-ons. Factor analysis can be a useful statistical method for identifying potential gaps and new dimensions for HRQoL instruments.