Myocardial infarction and prevalence of diabetes mellitus. Is increased casual blood glucose at admission a reliable criterion for the diagnosis of diabetes?

AIMS To investigate the prevalence of diabetes mellitus in patients with acute myocardial infarction and to determine whether casual blood glucose and haemoglobin A1c measured at admission could be used to diagnose diabetes mellitus. METHODS AND RESULTS A prospective study that included all patients with acute myocardial infarction hospitalized during a one-year period at a coronary care unit. Casual blood glucose was measured at admission, fasting blood glucose during the hospital stay and, if necessary for classification, 2-3 months after discharge. Haemoglobin A1c was measured once at admission. Of 305 patients included in the study, 285 could be classified into three groups: 21% of these had previously diagnosed diabetes, 4% had newly diagnosed diabetes and the remaining patients were categorized as non-diabetic. Casual blood glucose >or=11.1 mmol x l(-1)at admission was found in 12 patients with no previously known diabetes, but diabetes mellitus was confirmed in only six of these patients. Haemoglobin A1c showed considerable overlapping of values between the three groups of patients (i.e. patients with known diabetes mellitus, patients with newly diagnosed diabetes mellitus and non-diabetics). CONCLUSION One of four patients with acute myocardial infarction had diabetes mellitus. Increased casual blood glucose at admission was not a reliable measure to establish a diagnosis of diabetes and thus follow-up measures were necessary. Haemoglobin A1c was found to be an unreliable measure in the verification of diabetes.