The development and cross-national validation of the short health literacy for school-aged children (HLSAC-5) instrument.

Health literacy is an asset for and indicator of adolescents' health and wellbeing, and should therefore be monitored and addressed across countries. This study aimed to develop and validate a shorter version of the original 10-item health literacy for school-aged children instrument in a cross-national context, using data from the health behaviour in school-aged children 2017/18 survey. The data were obtained from 25 425 adolescents (aged 13 and 15 years) from seven European countries. Determination was made of the best item combination to form a shorter version of the health literacy instrument. Thereafter, the structural validity, reliability, measurement invariance, and criterion validity of the new 5-item instrument were examined. Confirmatory factor analysis showed a good model fit to the data across countries and in the total sample, confirming the structural validity (CFI = 0.995, TLI = 0.989, SRMR = 0.011, RMSEA = 0.031). The internal consistency of the instrument was at a good level across countries (α = 0.87-0.98), indicating that the instrument provided reliable scores. Configural and metric invariance was established across genders, ages, and countries. Scalar invariance was achieved for age and gender groups, but not between countries. This indicated that the factor structure of the scale was similar, but that there were differences between the countries in health literacy levels. Regarding criterion validity, structural equation modelling showed a positive association between health literacy and self-rated health in all the participating countries. The new instrument was found to be valid and reliable for the purposes of measuring health literacy among adolescents in a cross-national context.