Screening for overt diabetes by oral glucose tolerance test: stratification by fasting blood glucose and patients' age improve practicability of guidelines in cardiological routine.

Background/objectives: Guidelines recommend screening all patients with cardiovascular disease by oral glucose tolerance test (OGTT). Due to its time-consuming protocol, costs and overall inconvenience performance of OGTT is limited in cardiological routine. Thus, we aimed to identify easily available parameters that could help to reduce the numbers of OGTT needed.

Methods: OGTTs (n=1215) were performed in all patients without known type 2 diabetes mellitus (T2DM) that were submitted to the heart center Wuppertal with known or suspected coronary artery disease for an elective coronary angiography from January to October 2007.

Results: 31.4% had normal glucose tolerance; prediabetes was present in 50.7%, whereas 17.9% were newly diagnosed with T2DM. Thus, 998 OGTTs did not result in the new diagnosis of so far undiagnosed T2DM. Multiple logistic regression and receiver operated characteristic analyses demonstrated that fasting blood glucose (FBG)≥ 90 mg/dl and age ≥ 55 years were predictive for so far undiagnosed T2DM. Considering these two parameters 81.1% (=sensitivity) of so far undiagnosed T2DM patients would have been identified (specificity=63.4%) and the number of OGTTs could have been reduced from 1215 to 541.

Conclusions: About 70% of patients were newly diagnosed with impaired glucose metabolism. FBG ≥ 90 mg/dl and age ≥ 55 years were predictive for so far undiagnosed T2DM and OGTTs could be reduced by 55.5%. This should alleviate the implementation of the current guidelines in daily cardiological practice.