Introduction to the Diabetes Numeracy Test (DNT)
The Diabetes Numeracy Test (DNT) is a specialized assessment to evaluate the mathematical skills essential for effective diabetes self-management. Developed in 2008 by a multidisciplinary expert panel at the Vanderbilt Diabetes Research and Training Center, led by Mary Margaret Huizinga and her colleagues, the DNT was the first scale of its kind to specifically measure numeracy skills in the context of diabetes care. With over 230 citations, its importance is well-recognized in both clinical and research settings. This test assesses a patient’s ability to interpret blood glucose levels, calculate carbohydrate intake, and adjust insulin doses—tasks that are fundamental to daily disease management. Consequently, the DNT provides invaluable insights for clinicians aiming to identify educational needs and for researchers studying the relationship between health literacy and patient outcomes. This article provides a comprehensive overview of the DNT’s features, scoring, applications, and limitations.
Key Features of the Diabetes Numeracy Test (DNT)
Purpose and Use of the Diabetes Numeracy Test (DNT)
The primary purpose of the DNT is to assess the specific numeracy skills that patients with diabetes encounter in their daily self-care routines. These skills include understanding nutritional information, monitoring blood glucose, managing oral medications, and using insulin correctly. By identifying gaps in a patient’s numerical understanding, healthcare providers can tailor educational interventions and support, ultimately improving patient safety and glycemic control.
Target Population of the Diabetes Numeracy Test (DNT)
The researchers have designed the DNT for adults aged 18 and older with diabetes. However, certain exclusion criteria apply; the test is not recommended for patients with a corrected visual acuity of more than 20/50, or those with a diagnosis of significant dementia, psychosis, or blindness. Notably, a specialized 14-item version (DNT-14) has been developed and validated specifically for adolescents with type 1 diabetes.
Structure of the Diabetes Numeracy Test (DNT)
The original DNT consists of 43 items that cover two main areas: diabetes care domains and the underlying mathematical skills required.
The five diabetes care domains include:
- Nutrition (9 items)
- Exercise (4 items)
- Blood Glucose Monitoring (4 items)
- Oral Medication Use (5 items)
- Insulin Use (21 items)
These items require patients to utilize eight different types of numeracy skills, such as addition, multiplication, fractions, and multi-step mathematics. The response types include both multiple-choice and open-ended questions.
Scoring Method
The DNT employs a straightforward scoring system.
- Each of the 43 items is scored dichotomously as either correct (1) or incorrect (0), with no partial credit awarded.
- The total score represents the percentage of correct responses and ranges from 0% to 100%.
- There are no standard cut-off scores for interpretation; rather, the score is used to gauge a patient’s overall level of diabetes-related numeracy.
- Importantly, to simulate real-world conditions, administrators permit patients to use calculators and set no time limit for completion.
Administration Format
The DNT takes an average of 33 ± 13 minutes to complete and can be administered through a variety of flexible formats to suit different clinical and research environments. These include:
- Paper-based forms
- Digital (Online) platforms
- Mobile Apps
- Interview (In-person)
- Phone/Video call
The protocol requires basic training for personnel overseeing its administration to ensure consistency and accuracy.
Applications of the Diabetes Numeracy Test (DNT)
The DNT is a versatile tool with significant utility in several areas of diabetes care:
- Screening: It effectively identifies patients with low numeracy skills who may be at higher risk for poor self-management and adverse health outcomes.
- Treatment Planning: The results can guide clinicians in developing personalized education plans, simplifying medication regimens, and providing targeted support to address specific skill gaps.
- Research: The researchers widely use the DNT to investigate the links between numeracy, health literacy, and diabetes outcomes, as well as to evaluate the effectiveness of educational interventions.
Languages and Availability
The DNT now exists in several translated and validated languages to support its use in global research. Available versions include English, Arabic, and a shortened 15-item version in Spanish and Persian. Although the DNT is distributed under an open-access license, the authors at Vanderbilt University, who hold the copyright, require users to obtain permission.
Reliability and Validity of the Diabetes Numeracy Test (DNT)
The DNT is a highly reliable and valid instrument. The original validation study demonstrated excellent internal consistency, with a Kuder-Richardson 20 (KR-20) coefficient of 0.95, indicating that the items cohesively measure the construct of diabetes numeracy. Numerous validation studies, including those for the original English version, a Spanish version for Latinos, and an Arabic version, have further confirmed its strong psychometric properties.
Limitations and Considerations
Despite its strengths, the DNT has some limitations:
- Length: The 43-item original version can be lengthy for some patients, particularly in busy clinical settings.
- Cultural Bias: As with many assessment tools, there is a risk of cultural bias in the phrasing of questions.
- Language Barriers: Although several translations exist, its availability is not universal, which can be a limitation.
- Limited Validation: There may be limited validation studies for certain populations or shorter versions of the test.
Other Versions and Related Questionnaires
To address the limitation of length, researchers have developed several shorter versions of the DNT:
- Diabetes Numeracy Test-15 (DNT-15)
- Diabetes Numeracy Test-5 (DNT-5)
- Diabetes Numeracy Test-14 (DNT-14) for adolescents
- Diabetes Numeracy Test- 39 (DNT-39)
The DNT is often used alongside knowledge-based questionnaires, such as the Diabetes Knowledge Test (DKT), Diabetes Knowledge Questionnaire (DKQ) and the Patient Diabetes Knowledge Questionnaire (PDKQ), to provide a more comprehensive picture of a patient’s self-management capacity.
Additional Resources
For more information on the DNT and to access the full questionnaire, please visit the following resources:
- Original Validation Study: The foundational publication is available in the journal BMC Health Services Research.
- Questionnaire PDF.
- For Inquiries: For permission to use the scale, contact the first author, Dr. Mary Margaret Huizinga, at mary.margaret.huizinga@vanderbilt.edu.
Frequently Asked Questions (FAQ)
- Who can use the DNT?
Clinicians, researchers, and healthcare providers use the DNT for adult patients (18 and older) with diabetes to assess their numeracy skills related to self-management. - How long does it take to complete the DNT?
Patients typically take about 33 minutes to complete the full 43-item DNT, though this can vary. Shorter versions are available for quicker assessments. - How is the DNT administered?
Healthcare teams can administer the DNT via paper-based, digital (online), mobile app, or interview formats, offering significant flexibility. - Is there any cost to using the DNT?
The DNT requires permission for use, which can be obtained by contacting the authors at Vanderbilt University.
A Word from ResRef
The DNT is a pivotal tool for addressing numeracy gaps in diabetes care. Its short form (DNT-15) offers practical utility in clinical settings, directly linking poor numeracy to glycemic outcomes.
References
- Huizinga MM, Elasy TA, Wallston KA, Cavanaugh K, Davis D, Gregory RP, Fuchs LS, Malone R, Cherrington A, Dewalt DA, Buse J, Pignone M, Rothman RL. Development and validation of the Diabetes Numeracy Test (DNT). BMC Health Serv Res. 2008 May 1;8:96. doi: 10.1186/1472-6963-8-96. PMID: 18452617; PMCID: PMC2390531. Link.
- Alghodaier H, Jradi H, Mohammad NS, Bawazir A. Validation of a diabetes numeracy test in Arabic. PLoS One. 2017 May 4;12(5):e0175442. doi: 10.1371/journal.pone.0175442. PMID: 28472140; PMCID: PMC5417435. Link.
- White RO 3rd, Osborn CY, Gebretsadik T, Kripalani S, Rothman RL. Development and validation of a Spanish diabetes-specific numeracy measure: DNT-15 Latino. Diabetes Technol Ther. 2011 Sep;13(9):893-8. doi: 10.1089/dia.2011.0070. Epub 2011 Jun 29. PMID: 21714674; PMCID: PMC3160266. Link.
- Hasan S, Mahameed S, AlHariri Y. Translation and culture adaptation of the Simplified Diabetes Knowledge Test, the Literacy Assessment for Diabetes and the Diabetes Numeracy Test. Res Social Adm Pharm. 2020 Aug;16(8):1050-1056. doi: 10.1016/j.sapharm.2019.11.003. Epub 2019 Nov 6. PMID: 31744731. Link.
- Mulvaney SA, Lilley JS, Cavanaugh KL, Pittel EJ, Rothman RL. Validation of the diabetes numeracy test with adolescents with type 1 diabetes. J Health Commun. 2013;18(7):795-804. doi: 10.1080/10810730.2012.757394. Epub 2013 Apr 11. PMID: 23577642; PMCID: PMC3817720. Link.
