OBJECTIVES: We compared the measurement properties of two different proxy versions of EQ-5D-Y-3L (Y-3L) and EQ-5D-Y-5L (Y-5L) in caregivers of paediatric patients with asthma or eczema. Using the proxy-proxy version (P1), caregivers rate the child’s health from their (the proxy’s) point of view; using the proxy-patient version (P2), the caregivers are required to imagine how the child would rate their own health.

METHODS: We recruited paediatric asthma/eczema patients and their parents/legal guardians from the specialist outpatient clinics of two tertiary hospitals in Singapore. Patients completed Y-3L and Y-5L. Proxies completed either the P1 or P2 version of Y-3L and Y-5L. Asthma control was assessed using the Global Initiatve for Asthma (GINA) assessment while eczema severity was assessed by the clinicians using the validated Investigator Global Assessment for Atopic Dermatitis (vIGA-AD). A subset of patient-proxy dyads was reassessed after 101.3 ± 63.6 days. Known-groups validity, responsiveness to improvement, and patient-proxy agreement were assessed for both proxy versions of Y-3L and Y-5L using Y-3L index score (3L-Index), Y-5L level sum score (5L-LSS), and EQ VAS.

RESULTS: We included 328 child-proxy dyads (P1: 154 dyads; P2: 174 dyads). P2 demonstrated lower ceiling effects [P1: 53.90%-63.90%; P2: 47.13%-56.32%]. All P1-derived scores differed as expected between known groups defined by GINA or vIGA-AD but not all P2-derived scores differed as expected. P1/P2 standardized effect sizes for improvement were 0.48/0.21 for 3L-Index and -0.28/-0.42 for 5L-LSS. Patient-proxy agreement was low-to-moderate in both proxy versions (ICC range: 0.22-0.42). All proxy-reported scores indicated better health as compared to self-reported scores regardless of which proxy version was used.

CONCLUSIONS: In this population, neither proxy version was superior on the psychometric tests performed. Either version may be suitable for use depending on the purpose of the study they are to be used in. Further research is needed to confirm these results.