In self-monitoring a chronic condition, such as hypertension or diabetes, patients must understand and interpret whatever numbers or values they obtain. The influence of a patient's quantitative skills (numeracy) on the management of diabetes, for example, is only partially understood. Cavanaugh and coworkers examined the association between diabetes-related numeracy and glycemic control and other diabetes measurements in a cross-sectional survey at two primary care and two diabetes clinics at three medical centers. A total of 398 adult patients with type 1 or type 2 diabetes mellitus participated. The study assessed health literacy, general numeracy, and diabetes-related numeracy assessed by using the Rapid Estimate of Adult Literacy in Medicine; the Wide Range Achievement Test, 3rd edition; and the Diabetes Numeracy Test (DNT), respectively. The primary outcome was the most recent level of hemoglobin A1c. Additional measures were of diabetes knowledge, perceived self-efficacy of diabetes self-management, and self-management behaviors. The median DNT score was 65%. Common errors included misinterpreting glucose meter readings and miscalculating carbohydrate intake and medication dosages. Lower DNT scores were associated with older age, nonwhite race, fewer years of education, lower reported income, lower literacy and general numeracy skills, lower perceived self-efficacy, and selected self-management behaviors. Patients scoring in the lowest DNT quartile (score <42%) had a median hemoglobin A1c level of 7.6% compared with 7.1% in those scoring in the highest quartile. A regression analysis adjusted for age, sex, race, income, and other factors found a modest association between DNT score and hemoglobin A1c level.

WHAT THE STUDY MAY MEAN TO YOU AS A HEALTH CARE PROVIDER: The authors concluded that poor numeracy skills were common in patients with diabetes. Low diabetes-related numeracy skills were associated with worse perceived self-efficacy, fewer self-management behaviors, and possibly poorer glycemic control.

WHAT THE STUDY MAY MEAN TO YOU AS A PATIENT: The study showed that you must be able to read and interpret the numbers of whatever instrument you use to assess diabetes, hypertension, asthma, or any other chronic condition. Before your health care provider asks you to gather information on yourself, be certain that you know what data you are collecting and how you should use it in your daily effort to control your illness. The information can be useful to health care providers, but it can be invaluable to you. Any way that you can take steps to improve your control of an illness, the better it will be for you. Never hesitate to ask any questions if you are uncertain what you are supposed to do. If your health care provider asks you to record the information in a diary, be certain he or she has explained how you should do this task. The big thing, however, is that you make proper use of whatever data you gather to help yourself.

K Cavanaugh et al. Association of numeracy and diabetes control. Annals of Internal Medicine, 2008;148:737-746.