Screening questions to predict limited health literacy: a cross-sectional study of patients with diabetes mellitus.

PURPOSE Limited health literacy is increasingly recognized as a barrier to receiving adequate health care. Identifying patients at risk of poor health outcomes secondary to limited health literacy is currently the responsibility of clinicians. Our objective was to identify which screening questions and demographics independently predict limited health literacy and could thus help clinicians individualize their patient education. METHODS Between August 2006 and July 2007, we asked 225 patients being treated for diabetes at an academic primary care office several questions regarding their reading ability as part of a larger study (57% response rate). We built a logistic regression model predicting limited health literacy to determine the independent predictive properties of these questions and demographic variables. Patients were classified as having limited health literacy if they had a Short Test of Functional Health Literacy in Adults (S-TOFHLA) score of less than 23. The potential predictors evaluated were self-rated reading ability, highest education level attained, Single-Item Literacy Screener (SILS) result, patients' reading enjoyment, age, sex, and race. RESULTS Overall, 15.1% of the patients had limited health literacy. In the final model, 5 of the potential predictors were independently associated with increased odds of having limited health literacy. Specifically, patients were more likely to have limited health literacy if they had a poorer self-rated reading ability (odds ratio [OR] per point increase in the model = 3.37; 95% confidence interval [CI], 1.71-6.63), more frequently needed help reading written health materials (assessed by the SILS) (OR = 2.03; 95% CI, 1.26-3.26), had a lower education level (OR = 1.89; 95% CI, 1.12-3.18), were male (OR = 4.46; 95% CI, 1.53-12.99), and were of nonwhite race (OR = 3.73; 95% CI, 1.04-13.40). These associations were not confounded by age. The area under the receiver operating characteristic curve was 0.9212. CONCLUSIONS Self-rated reading ability, SILS result, highest education level attained, sex, and race independently predict whether a patient has limited health literacy. Clinicians should be aware of these associations and ask questions to identify patients at risk. We propose an "SOS" mnemonic based on these findings to help clinicians wishing to individualize patient education.