Validity and measurement invariance across sex, age, and education level of the French short versions of the European Health Literacy Survey Questionnaire

Background: Short versions of the European Health Literacy Survey (HLS-EU) questionnaire are increasingly used to measure and compare health literacy (HL) in populations worldwide. As no validated versions of these questionnaires have thus far appeared in French, this study aimed to study the psychometric properties of the French translation of the 16- and 6-item short versions (HLS-EU-Q16 and HLS-EU-Q6), including their measurement invariance across sex, age, and education level. Methods: A consensual French version of the HLS-EU-Q16 and HLS-EU-Q6 was developed by following the current recommendations for transcultural questionnaire adaptation. It was then completed by 317 patients recruited in waiting rooms of general practitioners in the Paris area (France). Structural validity was studied with the Rasch model for the HLS-EU-Q16 and confirmatory factorial analysis (CFA) for the HLS-EU-Q6. Concurrent and convergent validity, respectively, were assessed by scores on the Functional Communicative Critical Health Literacy (FCCHL) questionnaire and the physicians’ evaluations of their patient’s HL. Results: The 16 items of the HLS-EU-Q16 were Rasch homogenous but meaningful differential item functioning (DIF) was found across sex, age, and/or education level for eight items. The CFA model fit for the HLS-EU-Q6 was poor. The overall scores for both HLS-EU short versions correlated poorly with the FCCHL scores. Similarly, HL levels defined using either short-version score did not agree with physicians’ HL assessments. Conclusion: The French version of the HLS-EU-Q16 has acceptable psychometric properties, despite meaningful DIF for age, sex and education level and a poor discriminative power among subjects with average to high HL level. We recommend its use to measure HL in populations with sufficient reading skills to discriminate between subjects with low to average HL. Also, sensitivity analyses should be performed to evaluate the potential measurement bias due to DIF. Our results did not demonstrate the validity of the HLS-EU-Q6.