RESUMO
BACKGROUND: Health literacy is the ability to access to, understand, evaluate and use of essential health information to make basic health decisions. This study aimed to develop and psychometrically evaluate an instrument for measuring health literacy among adults (the Health Literacy Instrument for Adults - HELIA). METHODS: In addition to a literature review, a panel of specialists from different disciplines was formed to generate an item pool. Then, a framework was defined to develop the initial questionnaire based on a definition of health literacy and the most important global public health issues. The initial questionnaire contained 66 items. Next, 15 experts in public health were approached to assess content validity. Consequently, 19 items were removed and a provisional version of the questionnaire with 47 items was provided. Finally, a random sample of adults completed the questionnaire and psychometric properties of the instrument were assessed. RESULTS: Overall, 323 adults aged 18 to 65 years old completed the questionnaire. When the exploratory factor analysis was performed, 33 items were loaded, which indicated a 5-factor solution for the questionnaire that jointly explained 52.9% of the variance observed. The factors were as follows: access to information (6 items), reading (4 items), understanding (7 items), appraisal (4 items), and decision making/behavioral intention (12 items). Confirmatory factory analysis also indicated a good fit to the data for the five-latent structure (χ2/df = 1.60, SRMR = 0.049; RMSEA = 0.043; CFI = 0.98; NFI = 0.95; NNFI = 0.98 and GFI = 0.87). Additional analysis for internal consistency showed satisfactory results with Cronbach's alpha coefficients ranging from 0.72 to 0.89. Intraclass correlation coefficient (test-retest analysis) also showed acceptable stability for the questionnaire (ICC = 0.84). The mean score for health literacy as measured by the HELIA was 76.3 (SD = 15.1) out of 100 for the study sample. CONCLUSION: The findings suggest that the Health Literacy Instrument for Adults (HELIA) is a valid and reliable instrument for measuring health literacy. It is a short and easy-to-use instrument that could be applied in different settings.