Different Measures, Different Outcomes? A Systematic Review of Performance-Based versus Self-Reported Measures of Health Literacy and Numeracy

BSTRACT BACKGROUND Health literacy (HL) and numeracy are measured by one of two methods: performance on objective tests or self-report of one’s skills. Whether results from these methods differ in their relationship to health outcomes or use of health services is unknown. METHODS We performed a systematic review to identify and evaluate articles that measured both performance-based and self-reported HL or numeracy and examined their relationship to health outcomes or health service use. To identify studies, we started with an AHRQ-funded systematic review of HL and health outcomes. We then looked for newer studies by searching MEDLINE from 1 February 2010 to 9 December 2014. We included English language studies meeting pre-specified criteria. Two reviewers independently assessed abstracts and studies for inclusion and graded study quality. One reviewer abstracted information from included studies while a second checked content for accuracy. RESULTS We identified four “fair” quality studies that met inclusion criteria for our review. Two studies measuring HL found no differences between performance-based and self-reported HL for association with self-reported outcomes (including diabetes, stroke, hypertension) or a physician-completed rheumatoid arthritis disease activity score. However, HL measures were differentially related to a patient-completed health assessment questionnaire and to a patient’s ability to interpret their prescription medication name and dose from a medication bottle. Only one study measured numeracy and found no difference between performance-based and self-reported measures of numeracy and colorectal cancer (CRC) screening utilization. However, in a moderator analysis from the same study, performance-based and self-reported numeracy were differentially related to CRC screening utilization when stratified by certain patient–provider communication behaviors (e.g., the chance to always ask questions and get the support that is needed). DISCUSSION Most studies found no difference in the relationship between results of performance-based and self-reported measures and outcomes. However, we identified few studies using multiple instruments and/or objective outcomes.