Validation of Self-Reported Health Literacy Questions Among Diverse English and Spanish-Speaking Populations

Limited health literacy (HL) contributes to poor health outcomes and disparities, and direct measurement is often time-intensive. Self-reported HL questions have not been validated among Spanish-speaking and diverse English-speaking populations. To evaluate three self-reported questions:1 How confident are you filling out medical forms?;2 How often do you have problems learning about your medical condition because of difficulty understanding written information?; and3 How often do you have someone help you read hospital materials? Answers were based on a 5-point Likert scale. This was a validation study nested within a trial of diabetes self-management support in the San Francisco Department of Public Health. English and Spanish-speaking adults with type 2 diabetes receiving primary care. Using the Test of Functional Health Literacy in Adults (s-TOFHLA) in English and Spanish as the reference, we classified HL as inadequate, marginal, or adequate. We calculated the C-index and test characteristics of the three questions and summative scale compared to the s-TOFHLA and assessed variations in performance by language, race/ethnicity, age, and education. Of 296 participants, 48% were Spanish-speaking; 9% were White, non-Hispanic; 47% had inadequate HL and 12% had marginal HL. Overall, 57% reported being confident with forms somewhat or less. The confident with forms question performed best for detecting inadequate (C-index = 0.82, (0.77-0.87)) and inadequate plus marginal HL (C index = 0.81, (0.76-0.86); p < 0.01 for differences from other questions), and performed comparably to the summative scale. The confident with forms question and scale also performed best across language, race/ethnicity, educational attainment, and age. A single self-reported HL question about confidence with forms and a summative scale of three questions discriminated between Spanish and English speakers with adequate HL and those with inadequate and/or inadequate plus marginal HL. The confident with forms question or the summative scale may be useful for estimating HL in clinical research involving Spanish-speaking and English-speaking, chronically-ill, diverse populations.