Psychometric performance of the experimental EuroQol Toddler and Infant Populations (EQ-TIPS EV2.0) against developmental functioning evaluated by Bayley-III in rural Chinese infants and toddlers

The experimental EuroQol Toddler and Infant Populations version 2.0 was developed to address the scarcity of health-related quality of life (HRQoL) instruments for infants and toddlers. This study aimed to evaluate the psychometric performance of the EQ-TIPS against the Bayley Scales of Infant and Toddler Development, 3rd Edition (Bayley-III) in rural Chinese children. We analyzed data from a representative cross-sectional survey in rural Zhejiang, China. The sample comprised 591 children aged 6–24 months selected via multistage stratified sampling. Primary caregivers (77% mothers) completed the proxy-reported EQ-TIPS with a recall period of “today”. We compared parent proxy-reported EQ-TIPS responses with assessor-rated Bayley-III scores. Psychometric evaluation included response distribution, known-group validity (comparing EQ-TIPS scores across Bayley-III defined cognitive, motor, and language delay groups), and convergent validity (assessing correlations between EQ-TIPS movement with Bayley-III motor and EQ-TIPS communication with Bayley-III language). Analyses were stratified by age to assess developmental sensitivity across stages. Bayley-III identified 39.6%, 19.1%, and 41.6% of children as having cognitive, motor, and language delays, respectively. A ceiling effect was observed for EQ-TIPS, with 60.2% reporting the best health state. Known-group validity was supported: children with cognitive, motor, or language delays identified by the Bayley-III had significantly more problems reported in the corresponding EQ-TIPS eating, movement, and communication dimensions (all p values < 0.01), although effect sizes were small. Age-stratification showed that the EQ-TIPS communication dimension had moderate discriminative ability for language delays in toddlers (19–24 months) but was less sensitive in younger infants. Convergent validity between EQ-TIPS dimensions and Bayley-III composite scores was generally weak. This study provides the first psychometric evaluation of EQ-TIPS against clinical developmental assessment in Chinese infants and toddlers. EQ-TIPS demonstrated known-group validity with small effect sizes in differentiating children with and without developmental delays, particularly in the eating, communication, and movement dimensions. However, weak convergence with Bayley-III suggests that parent-reported HRQoL and clinical developmental functioning capture distinct constructs. Future studies should further evaluate the measurement properties of EQ-TIPS across diverse populations and clinical conditions, and compare its performance alongside other generic HRQoL instruments.