Diagnostic value of hemoglobin A1c and fasting plasma glucose levels in coronary artery bypass grafting patients with undiagnosed diabetes mellitus.

BACKGROUND: Early detection, diagnosis, and treatment of diabetes are of utmost importance in preventing diabetic complications and improving short- and long-term outcomes in patients undergoing coronary artery bypass grafting surgery. The aim of this study was to evaluate the ability of preoperative hemoglobin A1c (HbA(1c)) measurement, either alone or in combination with fasting plasma glucose (FPG), to detect glycometabolic disturbances among patients undergoing elective on-pump coronary surgery.

METHODS: A total of 166 patients who underwent elective isolated on-pump coronary surgery were included. Hemoglobin A1c and 8-hour FPG measurements were obtained by venous blood sampling on the day before the operation. After 1 month, an oral glucose tolerance test was performed in all discharged patients without known diabetes. The sensitivity and specificity for the diagnosis of diabetes were analyzed for FPG, HbA(1c), and for the combined use of HbA(1c) and FPG, in reference to the tolerance test results.

RESULTS: Sixty percent of patients without known diabetes were diagnosed as diabetes or prediabetes with glucose tolerance test. Compared with either test alone, combined use of FPG and HbA(1c) had higher sensitivity and specificity. Positive predictive values for FPG, HbA(1c), and combined use of these two factors were 83.6%, 94%, and 97%, respectively. The combined use had a sensitivity and specificity of 84.4% and 94.1%, respectively.

CONCLUSIONS: Fasting plasma glucose alone does not seem sufficient for diagnosing approximately half of the patients with dysglycemia. Our results suggest that the use of FPG and HbA(1c) measurements in combination may be a useful strategy to preoperatively identify coronary patients with unknown diabetes.