The high prevalence of unknown diabetes mellitus (DM) in patients with coronary disease and that the oral glucose tolerance test (OGTT) is the best diagnostic method in this context are well known. However, data about the incidence of DM in this population have not been well described. In the present study, we sought to determine the actual incidence of new-onset DM in patients with coronary disease using the OGTT. Our secondary objective was to validate a predictive model. We studied a series of 338 patients with coronary disease without known DM using the OGTT. After the OGTT, the patients were reclassified as normoglycemic, prediabetic, and unknown DM, according to the American Diabetes Association 2010 criteria. After 3 years of follow-up, the patients without DM were again reassessed using the OGTT. We then built a predictive model using the multivariate logistic regression method and validated it using the leave-one-out method. The final sample was 191 patients. The mean follow-up was 3.13 years. The overall incidence of DM was 43.6 cases/1,000 person-years (95% confidence interval [CI] 26.8 to 60.4). The incidence was significantly different between the initially normoglycemic patients (11.5%, 95% CI 2.3% to 31.8%) and the prediabetic patients (70.5%, 95% CI 42.7% to 98.3%; p <0.001). A risk model that included the glucose level 2 hours after challenge, glycosylated hemoglobin and triglyceride levels, and presence of noncoronary vascular disease showed good predictive capacity for incident DM (area under the curve 0.882, 95% CI 0.819 to 0.946; p <0.0001). In conclusion, the real incidence of new DM is very high in the coronary population, especially in those with prediabetes. It is necessary to use the OGTT for diagnosis, but we can optimize its indication using a risk model.
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