Self‐administered health literacy instruments for people with diabetes: systematic review of measurement properties

Aims The aims of this study were to identify all available self‐administered instruments measuring health literacy in people with diabetes and to determine the current instrument that is the most appropriate for applying to this population in both practice and research. Design A systematic review of measurement properties. Data sources MEDLINE, EMBASE and CINAHL electronic databases from their inception up to 28 March 2016. Review method The methodological quality of each included study was assessed using the COnsensus‐based Standards for the selection of health Measurement INstruments checklist. The reported results for measurement properties in the studies were assessed according to Terwee's quality criteria. Results Thirteen self‐administered instruments measuring health literacy in people with diabetes were identified, of which six (44%) were diabetes‐specific instruments. The instruments that covered the broadest contents of health literacy were the Health Literacy Scale and Health Literacy Questionnaire. The (test–retest) reliability, measurement error and responsiveness were not evaluated for any instrument, while internal consistency and hypothesis testing validity were the most frequently assessed measurement properties. Conclusions With the current evidence, the Health Literacy Scale may be the most appropriate instrument for patients with diabetes in practice and research. However, the structural validity of this scale needs to be further established, particularly in other language versions. It is also recommended to use the Diabetes Numeracy Test‐15 along with the Health Literacy Scale to complement the lack of numeracy measures in the Health Literacy Scale.