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Original Investigation
Oct 24, 2011

Cardiovascular Risk Prediction in Diabetic Men and Women Using Hemoglobin A1c vs Diabetes as a High-Risk Equivalent

Author Affiliations

Author Affiliations: Division of Preventive Medicine, Brigham and Women's Hospital, Boston, Massachusetts (Drs Paynter, Pradhan, Gaziano, Ridker, and Cook); F. Hoffmann-LaRoche Ltd, Basel, Switzerland (Dr Mazer); and Massachusetts Veteran's Epidemiology Research and Information Center (MAVERIC), VA Boston Healthcare System, Boston (Dr Gaziano).

Arch Intern Med. 2011;171(19):1712-1718. doi:10.1001/archinternmed.2011.351

Background It is unclear whether models that include hemoglobin A1c (HbA1c) levels only for diabetic patients improve the ability to predict cardiovascular disease (CVD) risk compared with the currently recommended classification of diabetes as a cardiovascular risk equivalent.

Methods A total of 24 674 women (including 685 diabetic participants at baseline) and 11 280 men (including 563 diabetic participants at baseline) were followed up prospectively for cardiovascular disease (CVD). One hundred twenty-five CVD events occurred in diabetic women (666 in nondiabetic women), and 170 events occurred in diabetic men (1382 in nondiabetic men). Models for CVD risk were generated separately for men and women using the traditional CVD risk factors with the addition of a term for HbA1c levels only for diabetic individuals. In diabetic participants, the resulting predicted risks were compared with classification of diabetes as a cardiovascular risk equivalent (10-year CVD risk of at least 20%).

Results In women, the models including HbA1c levels in diabetic participants improved the C statistic by 0.177 (P < .001) over the risk equivalence model and showed improved reclassification (net reclassification improvement [NRI] of 26.7% [P = .001]). In men, the improvements were more modest but still statistically significant (C statistic change of 0.039 [P = .02]; NRI of 9.2% [P = .04]). Including HbA1c levels also improved prediction over a dichotomous term for diabetes in women (NRI of 11.8% [P = .03]) but not in men.

Conclusions In both women and men with diabetes at baseline, we observed significant improvements in predictive ability of CVD risk using models incorporating HbA1c levels compared with classification of diabetes as a cardiovascular risk equivalent.