Comparison of the 50 and 100 Gram Oral Glucose Tolerance Test

Abstract

A series of two 100 gin. and two 50 gm. oral glucose tolerance tests were performed on each of ninety-six young, healthy, prison inmates under rigidly controlled experimental conditions. Mean blood glucose levels for fasting, one, two, and three hour-postchallenge determinations were compared between challenges. The interrelationships of these determinations were also compared between the two standard loading doses.Mean two-hour levels were 14 to 27 per cent higher after the larger challenge. With an appropriate conversion factor, the absolute difference in two-hour values could be equated. Thus, despite these unequal means, the diagnostic information obtained with either challenge at one and two hours does not differ. The fact that the one-hour determination was not related to loading dose size or obesity as expressed by the weight index [100 (weight)/height 2 ] and was highly correlated with the Tolerance Index, suggests that it is the preferable screening test for diabetes. Studies in other populations are needed to confirm this, however.Although mean levels at three hours were the same, the distribution of tolerance responses for this determination differed for the two challenges. An excess of both relative hypoglycemic and hyperglycemic responses occurred with the larger loading dose. These contrasting distributions suggest that the 100 gm., three-hour determination may possess unique diagnostic power to ascertain early chemical diabetes. Until adequate criteria of an abnormal three-hour response are established, however, this determination cannot be used as a screening test for diabetes.Physiologic variability for all specific determinations and the complete tolerance test were similar for both challenges. The fact that only a moderate degree of correlation was found between repeat tolerance responses greatly compromises the clinical values of a single glucose tolerance test.

Effects of size, time of day and sequence of meal ingestion on carbohydrate tolerance in normal subjects

“…Sequence of meal ingestion was without effect on any of the above variables. Most but not all previous studies have observed a progressive increase in plasma glucose concentrations with increasing glucose loads [1][2][3][4][5][6][7]. Although a significant association between meal size and post-prandial plasma glucose concentration was observed in the current studies when the data from all meals were assessed, the effect of meal size on meal tolerance was dependent on time of day.…”

“…To define the normal post-prandial glucose and hormonal responses under these conditions an examination of the effects of different sizes of meals, time of day of meal ingestion and sequence of ingestion of meals of different sizes on the factors involved in mixed meal tolerance would be required. Plasma glucose responses to varying amounts of orally administered glucose have been reported to correlate with the size of the glucose load in some studies [1][2][3][4][5] but not in others [6,7]. No correlation between meals of different sizes and post-prandial plasma glucose responses was observed in the only study to examine this relationship [8].…”

Relation Between Blood Glucose and Coronary Mortality Over 33 Years in the Whitehall Study

“…First, the findings are based on a 50-g OGTT, and a slightly differing doseresponse relationship might be obtained with a 75-g glucose load. A 100-g glucose load produces a 2hBG ϳ20% higher than a 50-g load (24); however, the difference in dose-response curve resulting from a 75-g load in comparison with that used here is not predictable. Fasting glucose was not measured.…”

International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes

“…Early attempts to standardize the definition of diabetes relied on the OGTT, but the performance and interpretation of the test were inconsistent and the number of subjects studied to define abnormal values was very small (1–6). Studies in the high-risk Pima Indian population that demonstrated a bimodal distribution of glucose levels following the OGTT (7,8) helped establish the 2-h value as the diagnostic value of choice, even though most populations had a unimodal distribution of glucose levels (9).…”