Increasing use of the two-hour postprandial blood glucose test in screening for diabetes detection has resulted in an increased number of borderline oral glucose tolerance tests, and the dilemma of their proper interpretation. In spite of controlled pretest precautions, the two-hour-lag oral glucose tolerance test with fasting normoglycemia may lack specificity as an index of latent diabetes. The intravenous tolbutamide test as a supplemental test may offer greater specificity in the diagnosis of early diabetes, and a recent oral modification of this test offers added convenience and safety without sacrificing reliability.
This is a report based upon the oral test performed on a group of 105 hospital patients selected because each had an elevated second-hour blood sugar level with fasting normoglycemia on a standard oral glucose tolerance test. An abnormal oral sodium tolbutamide test was elicited in fifty-two of this group of 105, and the abnormal tolbutamide test correlated significantly with a positive family history of diabetes, an obstetrical history suggestive of diabetes, or those patients with an elevated third-hour blood sugar level on oral glucose tolerance. In only six of the 105 patients studied were the results of the oral sodium tolbutamide tests classified as borderline between normal and abnormal by the criteria of Boshell and Vecchio.
We conclude that the oral sodium tolbutamide test seems to be a valuable additional study in the appraisal of minimally abnormal oral glucose tolerance results at least in the presence of obesity, liver disease, hyperthyroidism, uremia, myocardial infarction, chronic pancreatitis, spontaneous hypoglycemia, and lymphomas and related neo-plasia representing the major disease categories in our study group.