Testing a single item screener to support family doctors in identifying patients with limited health literacy: convergent validity of the SILS and the HLS-EU-Q16.

Background: Low health literacy (HL) is associated with reduced disease self-management skills, worse health outcomes, an increased number of hospitalizations, more frequent use of the emergency room and less utilization of preventive services. To support patients with low HL it is crucial to identify affected patients. HL is a multidimensional construct, which covers different skills and abilities to make informed health decisions. Validated brief screening tools to assess health-literacy-related skills or abilities in primary care settings are currently not available in German. This study aimed to validate a single item screener developed in the US for the German primary care setting.

Methods: Our study used cross-sectional data from a survey among mainly chronically ill patients (n = 346) conducted in family practices in the state of North Rhine-Westphalia. We explored the convergent validity between a single item literacy screener (SILS) and the HLS-EU-Q16. The SILS measures functional HL by asking patients about their need for help when reading information materials. The HLS-EU-Q16 is a multidimensional HL measure frequently used for research purposes in Germany. Associations between the two instruments were examined using Spearman's correlations and regression analyses. The diagnostic performance of the SILS relative to the HLS-EU-Q16 was assessed using receiver operator curves (ROC).

Results: The SILS had a statistically significant correlation with the HLS-EU-Q16 (Spearman ρ: 0.35) and explained 26% of its total variance. Stratified analyses of the convergent validity between both instruments by age, sex, migration background, education level and chronic disease status showed moderate statistically significant correlations in all subgroups (range: 0.223 to 0.428). With an area under the curve of 0.66, the receiver operator curve indicated a satisfactory diagnostic performance of the SILS relative to the HLS-EU-Q16.

Conclusions: The SILS provided an acceptable initial assessment of HL limitations among a heterogeneous population of mainly chronically ill patients in a primary care setting. With only one item, the SILS can be a short and effective tool for routine use in primary care and specialized care settings. Future research should test the SILS in other populations and pilot applications of the SILS in routine care.