Prevalence of undetected diabetes mellitus in invasive and interventional cardiology. Silent diabetes in the catheterization laboratory

In most randomized controlled trials on revascularization therapy for patients with ischemic coronary artery disease (CAD), the diabetes prevalence ranges between 15% and 35%. However, the true prevalence of diabetes is probably considerably underestimated in these trials. The European heart survey diabetes and the heart published in 2004 supplied strong evidence that there are many additional cases of undetected prediabetics and diabetics in any cardiology patient cohort. The long-term outcome of newly detected diabetics was found to be comparable to patients with already known diabetes mellitus. With this in mind, the Dresden silent diabetes study investigated the prevalence of undetected diabetes mellitus by oral glucose tolerance testing (OGTT) and comparative HbA1c sampling in 1,015 patients admitted for coronary angiography. Patients with known diabetes were excluded from the study. According to the OGTT only 513 patients (51%) were classified with normal glucose tolerance (NGT), 10 (1%) with isolated impaired fasting glucose (IFG), 349 (34%) with impaired glucose tolerance (IGT) and 143 (14%) were diagnosed with newly detected diabetes mellitus (DM). According to the HbA1c measurements 588 patients (58%) were classified as normal, 385 (38%) as borderline and only 42 (4%) were diagnosed with diabetes (DM). There was a significant correlation between the extent of CAD and glycemic status as defined by the OGTT. The number of patients with IGT and diabetes increased with the extent of CAD (IGT group p < 0.001, diabetes group p=0.01). However, no such correlation was observed when glycemic status was defined by HbA1c testing. Based on these results an OGTT should be routinely performed in patients with known or suspected coronary artery disease undergoing coronary angiography for diagnosis of diabetes, as HbA1c measurements alone appear to miss a substantial proportion of patients. These findings are of high clinical relevance with regard to optimal coronary revascularization procedure chosen in catheterization laboratories, preferably drug-eluting stents in cases of diabetes mellitus or newly detected diabetes mellitus and preferably coronary bypass surgery in diabetics with multi-vessel disease and high SYNTAX scores.