Validation of the Assessments of Adult Health Literacy: a Rasch measurement model approach

Health literacy (HL) is implicated in medical adherence, preventive health, mental health help-seeking, and health decision-making. HL includes three core areas/qualities: functional, interactive/communicative, and critical. Though HL is important in health and health decision-making, research on HL is relatively limited, with most research focused on functional HL. A contributing factor to this research gap is the lack of interactive and critical HL assessments. To address this gap, this study modified and assessed the validity of the Assessments of Adolescent Health Literacy, test-based assessments of functional, interactive, and critical HL, in an adult sample. Adults (n = 2346) completed a measurement battery that included the modified Assessments of Adult Health Literacy (AAHL-Adult) item bank (12 functional, 15 interactive, and 9 critical HL questions), Newest Vital Sign, Single-Item Literacy Scale, demographics, and questions about HL-related behaviours. The assessments were evaluated and validated using Rasch measurement models. Convergent and criterion validity were assessed. The final 6-item functional, 7-item interactive, and 7-item critical HL assessments and their composite (20 items) fit their respective Rasch models. Item-level invariance was established for gender, race, ethnicity, education, and age across all assessments. Good convergent validity with the Newest Vital Sign and Single-Item Literacy Scale and good criterion validity with the HL-related behaviours were observed for all assessments. The AAHL-Adult is the first test-based instrument validated in USA that includes assessments of all three core qualities of HL. These assessments have utility across multiple settings, including public health program planning and evaluation, intervention development and evaluation, and clinical settings.