Abnormal glycemic profiles by CGMS in obese first-degree relatives of type 2 diabetes mellitus patients.

INTRODUCTION: The conventionally used oral glucose tolerance test (OGTT) has been the mainstay for diagnosis of diabetes and prediabetes. However, recent studies have indicated that a continuous glucose monitoring system (CGMS) could detect impaired glycemia much earlier than OGTT, especially in certain groups. We aimed to study the 24-h glucose profile of high-risk obese first-degree relatives of type 2 diabetes patients by CGMS and ascertain if it was better than OGTT for early detection of type 2 diabetes. SUBJECTS AND METHODS: CGMS data of 20 subjects each in normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and newly detected diabetes mellitus (NDDM) groups were obtained. We considered minimum, maximum, mean, and range of glucose levels as well as number, duration, and area under the curve (AUC) for excursions. RESULTS: We found three (15%) NGT, seven (35%) IFG, and eight (40%) IGT subjects showed excursions in the diabetes range, whereas 18 (90%) NGT and 17 (85%) pure IFG subjects showed excursions in the IGT range. The maximum glucose values for NGT and IFG subjects were 176.0±41.4 mg/dL and 186.5±39.3 mg/dL, respectively, which is much above the present 2-h OGTT cutoff limit of 140 mg/dL. However, the average number of excursions and AUC of excursions did not differ significantly among the NGT, IFG, and IGT groups. The differences in the duration of excursion between NGT subjects with IFG values and NGT subjects with IGT values were statistically significant for an excursion limit of 140 mg/dL. However, this did not differ significantly between the IFG and IGT groups. CONCLUSIONS: CGMS indicated the presence of significant dysglycemia in first-degree relatives of diabetes patients without diabetes who were centrally obese. Hence it could be useful for early identification of individuals at greater risk of diabetes. A deranged glycemic profile may precede onset of overt diabetes by a long time, which may partly explain why some patients with new-onset type 2 diabetes or even prediabetes present with vascular complications at the outset.