Background: A national health literacy scale was developed in China in 2012, though no studies have validated it. In this investigation, we assessed the reliability, construct validity, and measurement invariance of that scale.
Methods: A population-based sample of 3731 participants in Hunan Province was used to validate the Chinese Resident Health Literacy Scale based on item response theory and classical test theory (including split-half coefficient, Cronbach's alpha, and confirmatory factor analysis). Measurement invariance was examined by differential item functioning.
Results: The overall Cronbach's alpha of the scale was 0.95 and Spearman-Brown coefficient 0.94. Confirmatory factor analysis showed that the test measured a unidimensional construct with three highly correlated factors. Highest discrimination was found among participants with limited to moderate health literacy. In all, 64 items were selected from the original scale based on factor loading, Pearson's correlation coefficient, and discrimination and difficulty parameters in item response theory. Measurement invariance was significant but slight. According to the two-level linear model, health literacy was associated with education level, occupation, and income.
Conclusions: The 2012 national health literacy scale was validated, and 64 items were selected based on classical test theory and item response theory. The revised version of the scale has strong psychometric properties with minor measurement invariance.