Diabetes
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Comparative Study
Comparison of the value of the two- and one-hour glucose levels of the oral GTT in the diagnosis of diabetes in Pima Indians.
In many population and screening studies of diabetes, the one-hour glucose level of the GTT has been used to define the diabetic status of subjects. The one-hour postglucose load determination has been preferred over the two-hour value by many investigators primarily because of convenience and justified on the basis of the high correlation between the two values. Venous plasma glucose levels, one and two hours after 75-gm. carbohydrate load, were determined on over 1600 Pima Indians. ⋯ The reproducivility of the GTT taken one to three weeks apart in a sample of ninety-nine Pima Indians showed that the two-hour level was superior to the one-hour level as measured by the mean values of the absolute difference between log GTT levels for test and retest values. The one-hour measurements also gave more disagreements between the classifications of diabetic status than the two-hour test values. If a single measure of glucose tolerance is to be selected for the diagnosis of diabetes among Pima Indians, these data provide a mathematical rationale for preferring the two-hour level to the one-hour determination.