Validation of a combined health literacy and numeracy instrument for patients with type 2 diabetes Huabin Luo a, *, Shivajirao P. Patil b , Qiang Wu c , Ronny A. Bell a , Doyle M. Cummings b , Alyssa D. Adams b , Bertha Hambidge b , Kay Craven b , Fei Gao a a Department of Public Health, Brody School of Medicine, East Carolina University, USA b Department of Family Medicine, Brody School of Medicine, East Carolina University, USA c Department of Biostatistics, College of Allied Health Sciences, East Carolina University, USA A R T I C L E I N F O Article history: Received 26 March 2018 Received in revised form 17 May 2018 Accepted 20 May 2018 Keywords: Health literacy Numeracy Measure Diabetes A B S T R A C T 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. Published by Elsevier B.V. 1. Introduction Health literacy is defined as “the degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions” [1]. Health numeracy is defined as “the degree to which individuals have the capacity to access, process, interpret, commu- nicate, and act on numerical, quantitative, graphical, bio-statistical, and probabilistic health information needed to make effective health decisions” [2]. Both low health literacy and low health numeracy have been associated with poor health outcomes [3–5]. Further, low levels of health literacy and numeracy are common among patients with diabetes and are associated with poor glycemic control, lower self-care activities, lower self-efficacy, and worse communication with healthcare providers [6–8]. The prevalence of diabetes has increased rapidly in the US [9]. In 2015, an estimated 30.3 million people, or 9.4% of the US population, had diabetes [9]. The serious health challenges facing people with diabetes include heart disease, stroke, kidney disease, blindness, and foot amputation [10]. The total estimated cost of diagnosed diabetes in 2017 is $327 billion, including $237 billion for direct medical costs and $90 billion for lost productivity [11]. Successful management of diabetes requires sufficient literacy and numeracy skills. Thus, the measurement of health literacy and numeracy is crucial to address these health challenges in this population. Continuous efforts have been made to develop instruments of health literacy, both subjective and objective tests, including diabetes-specific measurement [12–14]. The Short Test of Func- tional Health Literacy in Adults (S-TOFHLA), a non-diabetes specific instrument, has been used in previous studies to measure health literacy in patients with diabetes [15]. However, limitations of the S-TOFHLA include limited assessment of numeracy and reading skills [12]. Other instruments have additional limitations, such as increased participant burden and the potential for discomfort and embarrassment from the objective measures [12]. For example, the Diabetes Numeracy Test (DNT) and the Wide Range Achievement Test (WRAT) both require a longer administration time [12]. Furthermore, patients prefer subjective tests and indicate they are more likely to take these tests, compared with the objective tests that require mathematical calculations or test content knowledge * Corresponding author at: Department of Public Health, Brody School of Medicine, East Carolina University, 600 Moye Boulevard, Greenville, NC 27834, USA. E-mail address: Luoh@ecu.edu (H. Luo). https://doi.org/10.1016/j.pec.2018.05.017 0738-3991/Published by Elsevier B.V. Patient Education and Counseling xxx (2018) xxx–xxx G Model PEC 5966 No. of Pages 6 Please cite this article in press as: H. Luo, et al., Validation of a combined health literacy and numeracy instrument for patients with type 2 diabetes, Patient Educ Couns (2018), https://doi.org/10.1016/j.pec.2018.05.017 Contents lists available at ScienceDirect Patient Education and Counseling journal homepage: www.else vie r.com/locate /pateducou