Comparing HbA1c, fasting and 2-h plasma glucose for screening for abnormal glucose regulation in patients undergoing coronary angiography.

Background: We aimed to investigate the prevalence of undiagnosed abnormal glucose regulation (AGR, including diabetes and prediabetes) in patients undergoing coronary angiography (CAG) by using both glycated hemoglobin (HbA1c) and oral glucose tolerance test (OGTT) to screen, and to compare the performance of fasting plasma glucose (FPG), 2-h plasma glucose (2hPG), and HbA1c for screening for AGR.

Methods: Eligible patients were adults without known diabetes who were admitted for CAG. Patients' glucose regulation status was defined by conducting HbA1c and OGTT 2-4 weeks after hospital discharge. The performance of FPG, 2hPG, and HbA1c for detecting AGR was evaluated using receiver operating characteristic (ROC) analysis.

Results: A total of 689 subjects were included. According to OGTT, the prevalence rates of diabetes and prediabetes were 19.9% and 41.7%, respectively. The corresponding values were 28.0% and 60.4%, respectively, when HbA1c was adopted as a diagnostic criterion in addition to OGTT. For detecting diabetes, the area under the ROC curve (AUC) was higher for HbA1c than for FPG (0.87 vs. 0.80, p=0.005), but was not significantly different from that for 2hPG (0.87 vs. 0.88, p=0.58). For detecting AGR, the AUC was higher for HbA1c than for either FPG (0.94 vs. 0.74, p<0.001) or 2hPG (0.94 vs. 0.83, p<0.001).

Conclusions: Using HbA1c and OGTT to screen, we reported an extremely high prevalence of previously undiagnosed AGR (28.0% diabetes and 60.4% prediabetes) in patients admitted for CAG. HbA1c may be adopted as an alternative to OGTT for screening for AGR in patients undergoing CAG.