Bayley III in Vietnamese children: lessons for cross-cultural comparisons.

Background: There are limited psychometric reports of construct validity following adaptation of the Bayley Scales of Infant and Toddler Development 3 rd edition (Bayley III). This paper aims to demonstrate a process of assessing reliability, validity, and gender equivalence of the adapted tool for Vietnamese children. Methods: We evaluated cognitive, fine motor, gross motor, expressive communication and receptive communication subtests of the adapted tool in 267 healthy urban Vietnamese children. Subsets of participants were used to evaluate inter-observer and test-retest reliability. Confirmatory factor analysis (CFA) was carried out to evaluate construct validity and measurement invariance between genders. Results: The adaptation demonstrated good inter-observer and test-retest reliability. CFA indicated that a construct representing a single underlying factor showed the best fit, although relationships between the observed scores and the latent traits underlying the scores varied between age groups. Within age groups, relationships between observed scores and these factors were not significantly influenced by gender. Conclusions: The Vietnamese Bayley III demonstrated good internal consistency and reliability. A latent structure with one general factor and additional residual correlations that change with age is supported by the theoretical understanding of child development. This is the first study to demonstrate gender invariance by age group. This adaptation is suitable for further research studies in urban Vietnamese children, but further work is needed to extend its applicability more broadly across Vietnam.