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

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.