Describing progression of health literacy skills: Establishing the HLS-Q12 cut-off scores

Abstract

Background The self-reported European Health Literacy Survey Questionnaire (HLS-EU-Q47) is a widely used health literacy measure. Based on confirmatory factor analyses and Rasch-modelling, the short form HLS-Q12 was developed to meet the Rasch unidimensional measurement model expectations. After its publication, there has been a worldwide call to identify HLS-Q12 cut-off scores and establish clearly delineated standards in terms of the skills assessed. This study therefore aims to identify the HLS-Q12 scores associated with statistically distinct levels of proficiency and construct a proficiency scale that expresses progression – what individuals typically know and can do at increasingly more sophisticated levels of health literacy. Methods We applied the unidimensional Rasch measurement model for polytomous items to responses from 900 randomly sampled individuals and 388 individuals with type 2 diabetes. Using Rasch-based item calibration, we constructed a proficiency scale by locating the ordered item thresholds along the scale; by applying Wright’s method for the maximum number of strata, we determined the cut-off scores for significantly different levels. By directly referring to item content that people who reached the cut-off scores view as ‘easy’, we could describe these gradually more advanced levels of health literacy. Results We identified statistically distinct levels of health literacy at the empirically identified cut-off scores 27, 33 and 39 and confirmed them by analysing the responses from individuals with diabetes. Individuals who reach these cumulative benchmarks of marginal, intermediate and advanced literacy can typically access, appraise and apply information relevant to stay healthy, improve health and critically judge health claims and compare treatments, respectively. Conclusions By revealing progression in health literacy, we extended the current models of health literacy and inform policy-makers aiming to bridge literacy gaps. Determining how to best adapt information to patients’ literacy level and thereby assist them in managing their own health is a significant clinical outcome. A substantial methodological consequence is the inevitability of Rasch modelling in measurement. We also found that Wright’s method identified rating scale cut-off scores consistently across independent samples. To unveil sources of potential biases, threats to validity and imprecision of benchmarks, replicating our study in other contexts is required.