The American Diabetes Association (ADA) has released a Standards of Medical Care in Diabetes Position Statement for 2008 (1). In this document, it is stated that aspirin therapy should be used as a primary prevention strategy in diabetic patients at increased cardiovascular (CV) risk, including those who are >40 years old or have additional risk factors. The recommendation is based on evidence graded “A,” which is defined by the ADA as “evidence from well-conducted, randomized controlled trials that are adequately powered or compelling nonexperimental evidence.” As this indication seemed very broad, we attempted to examine to whom it applies. From our cohort of 1,093 type 2 diabetic outpatients followed at the Endocrine Division of Hospital de Clínicas de Porto Alegre (Porto Alegre, Brazil), all patients with known cardiovascular disease were excluded. Of the remaining 680 patients suitable for primary prevention, 97.5% had an indication of aspirin therapy according to the ADA criteria. Based on current evidence, the balance between expected benefits and risks of aspirin therapy in the diabetic population is doubtful, especially in the low-risk group.

To evaluate how many of our patients qualified for the low-risk category, we stratified patients by 10-year risk of developing a cardiovascular event into low-risk (≤7%), intermediate-risk (7–14%), and high-risk (≥14%) groups using the UK Prospective Diabetes Study Risk Engine (2) and the Framingham Risk Score (3). There were 24.8 and 13.8% low-risk, 27.2 and 24.8% intermediate-risk, and 48.1 and 61.4% high-risk patients by UK Prospective Diabetes Study Risk Engine and Framingham Risk Score criteria, respectively. The discrepancies between estimates of who should receive aspirin reflect the uncertainty that surrounds the subject of using aspirin for primary prevention in diabetic patients. As far as we know, there is just one large randomized controlled trial (4) evaluating the use of aspirin in diabetic patients exclusively for primary prevention, the results of which do not support the ADA recommendation. Assuming that a 10% risk reduction from aspirin therapy in diabetic patients does exist, it would be necessary to treat at least 143 low-risk patients for 10 years to prevent one cardiovascular event, while given a 1.5% risk of major bleeding, 1 patient would be harmed for every 67 treated. The ADA criteria do not seem to discriminate within the spectrum of risk that comprises the population of diabetic patients suitable for primary prevention. Furthermore, the substrate for indicating aspirin as a grade A recommendation for primary prevention is based on data from nondiabetic subjects and from studies of diabetic patients in which statistically nonsignificant benefits were shown. We think that these two points should be clearly stated, with physicians being encouraged to stratify risk and to not prescribe aspirin for primary prevention in low-risk patients.

1.
American Diabetes Association: Standards of medical care in diabetes—2008 (Position Statement).
Diabetes Care
31
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2008
2.
Stevens RJ, Kothari V, Adler AI, Stratton IM: The UKPDS risk engine: a model for the risk of coronary heart disease in Type II diabetes (UKPDS 56).
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3.
Wilson PW, D'Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB: Prediction of coronary heart disease using risk factor categories.
Circulation
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4.
Sacco M, Pellegrini F, Roncaglioni MC, Avanzini F, Tognoni G, Nicolucci A: Primary prevention of cardiovascular events with low-dose aspirin and vitamin E in type 2 diabetic patients: results of the Primary Prevention Project (PPP) trial.
Diabetes Care
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2003