Validation of a combined health literacy and numeracy instrument for patients with type 2 diabetes.

Objectives: This study aimed to validate a new consolidated measure of health literacy and numeracy (health literacy scale [HLS] plus the subjective numeracy scale [SNS]) in patients with type 2 diabetes (T2DM).

Methods: A convenience sample (N = 102) of patients with T2DM was recruited from an academic family medicine center in the southeastern US between September-December 2017. Participants completed a questionnaire that included the composite HLS/SNS (22 questions) and a commonly used objective measure of health literacy-S-TOFHLA (40 questions). Internal reliability of the HLS/SNS was assessed using Cronbach's alpha. Criterion and construct validity was assessed against the S-TOFHLA.

Results: The composite HLS/SNS had good internal reliability (Cronbach's alpha = 0.83). A confirmatory factor analysis revealed there were four factors in the new instrument. Model fit indices showed good model-data fit (RMSEA = 0.08). The Spearman's rank order correlation coefficient between the HLS/SNS and the S-TOFHLA was 0.45 (p < 0.01).

Conclusions: Our study suggests that the composite HLS/SNS is a reliable, valid instrument.