Development and validation of the Diabetes Numeracy Test (DNT)

Abstract

BackgroundLow literacy and numeracy skills are common. Adequate numeracy skills are crucial in the management of diabetes. Diabetes patients use numeracy skills to interpret glucose meters, administer medications, follow dietary guidelines and other tasks. Existing literacy scales may not be adequate to assess numeracy skills. This paper describes the development and psychometric properties of the Diabetes Numeracy Test (DNT), the first scale to specifically measure numeracy skills used in diabetes.MethodsThe items of the DNT were developed by an expert panel and refined using cognitive response interviews with potential respondents. The final version of the DNT (43 items) and other relevant measures were administered to a convenience sample of 398 patients with diabetes. Internal reliability was determined by the Kuder-Richardson coefficient (KR-20). An a priori hypothetical model was developed to determine construct validity. A shortened 15-item version, the DNT15, was created through split sample analysis.ResultsThe DNT had excellent internal reliability (KR-20 = 0.95). The DNT was significantly correlated (p < 0.05) with education, income, literacy and math skills, and diabetes knowledge, supporting excellent construct validity. The mean score on the DNT was 61% and took an average of 33 minutes to complete. The DNT15 also had good internal reliability (KR-20 = 0.90 and 0.89). In split sample analysis, correlations of the DNT-15 with the full DNT in both sub-samples was high (rho = 0.96 and 0.97, respectively).ConclusionThe DNT is a reliable and valid measure of diabetes related numeracy skills. An equally adequate but more time-efficient version of the DNT, the DNT15, can be used for research and clinical purposes to evaluate diabetes related numeracy.

Development and Validation of a Spanish Diabetes-Specific Numeracy Measure: DNT-15 Latino

“…16 The original DNT was designed for Englishspeaking patients and initially contained 43 items assessing numeracy skills applied to nutrition, exercise, glucose monitoring, oral medications, and insulin use. Items require respondents to perform addition and subtraction, understand fractions, divide, understand numerical hierarchy, and perform multistep calculations.…”

“…A shortened, 15-item version of this instrument demonstrated strong psychometric properties while covering all the skills tested by the 43-item version and has been recommended for use among English-speaking patients with diabetes. 13,16,17 This shortened version of the DNT provided the content that was translated into the DNT-15 Latino.…”

Clinician Numeracy: Use of the Medical Interpretation and Numeracy Test in Foundation Trainee Doctors

“…A question taken from the Diabetes Numeracy Test (Huizinga et al 2008) had been designed to ask diabetic patients to work out how much carbohydrate (number of cookies) was needed to cover a period of exercise, and 19/135 (14%) of the FTs answered this question incorrectly. This result raises concerns not just about the FTs' basic computational skills, but also about their ability to advise patients on diabetes management.…”

Clinician Numeracy: The Development of an Assessment Measure for Doctors

“…People with low health numeracy are less likely to access healthcare information; they struggle to understand data related to the risks and benefits of medical intervention, are less able to manage chronic health conditions, and are less likely to comply with treatment (Schwartz et al 1997;Estrada et al 2004;Apter et al 2006;Gigerenzer et al 2007;Huizinga et al 2008;Woloshin et al 2008;Reyna et al 2009). Healthcare professionals must access, interpret and communicate medical information accurately; this necessity is fundamental both to shared decisionmaking and to informed consent.…”