Do the Oral and Intravenous Glucose Tolerance Tests Provide Similar Diagnostic Information in Patients with Chemical Diabetes Mellitus?

In order to evaluate the diagnostic reliability of the oral glucose tolerance test (OGTT) and the intravenous glucose tolerance test (IVGTT), the results of these two teats have been-compared both to each other as well as to a third test of carbohydrate tolerance termed the pancreatic suppression test (PST), in forty-five subjects. When results of the IVGTT and OGTT are compared, there is a 40 per cent incidence of discordance in the diagnosis of diabetes mellitus. There is no significant correlation between the results of the PST and the IVGTT, but a significant correlation is obtained between results of the PST and the OGTT (P < 0.01). Furthermore, the PST could not detect differences between patients classified as normal or diabetic on the basis of the IVGTT, but differences could be detected between subjects divided into diabetic or normal on the basis of the OGTT (P < 0.001). Although neither test is an ideal diagnostic tool, our results suggest that the OGTT is more meaningful than its counterpart in estimating the efficiency of glucose disposal in patients with mild abnormalities of glucose tolerance.