Cross-national validation and measurement invariance of the HLS-EU-Q6 in Latin America: Evidence from adults in Ecuador, Peru and Venezuela

Background Health literacy is a key determinant of population health, yet evidence on the cross-national validity of brief health literacy instruments in Latin America remains limited. This study evaluated the psychometric properties and measurement invariance of the Health Literacy Survey European Questionnaire–Short Form (HLS-EU-Q6) among adults from Ecuador, Peru, and Venezuela. Methods A cross-sectional psychometric validation study was conducted in 2,034 adults from Venezuela (n = 957), Ecuador (n = 617), and Peru (n = 460). Exploratory and confirmatory factor analyses were performed using split-sample validation. Reliability was assessed using Cronbach's alpha, McDonald's omega, composite reliability, and average variance extracted. Measurement invariance was examined across countries and sociodemographic groups and known-groups validity was evaluated using Welch analyses of variance. Results The HLS-EU-Q6 showed a stable unidimensional structure with satisfactory reliability (α = .830; ω = .832; composite reliability = .866) and adequate convergent validity (average variance extracted = .519). Configural and metric invariance were supported across countries, whereas scalar invariance was not, indicating that observed score differences cannot be interpreted as equivalent differences in underlying health literacy. In contrast, full invariance was supported across educational level, scalar invariance across age groups, and partial scalar invariance across sex. Known-groups validity was supported by higher health literacy among participants with higher educational attainment and older age. Conclusions The HLS-EU-Q6 is a reliable and valid instrument for assessing global health literacy within Ecuador, Peru, and Venezuela. However, the absence of scalar invariance limits direct comparisons of observed scores across countries. These findings support the use of country-specific normative values and highlight the importance of evaluating measurement invariance before health literacy instruments are applied in multinational surveillance, programme evaluation, or cross-country public health research.