Glucose metabolism in children with renal failure: oral or intravenous glucose tolerance.

There is debate about the most suitable test for investigation of glucose tolerance in children with chronic renal failure. We therefore studied the agreement between the two most commonly used glucose tolerance tests in 33 children with chronic renal failure (mean age 10.9+/-5.3 years, median GFR was 24 ml/min/1.73 m2). All children underwent an oral glucose tolerance test (OGTT) with blood sampling up to 180 minutes and after an oral load of 1.75 g/kg and a standard intravenous glucose tolerance test (IVGTT) using 0.5 g/kg i.v. The two tests were performed at an interval of 23+/-5 days, with 9 patients having the OGTT before and 24 after the IVGTT. In order to account for the differing glucose load, a subgroup of 19 patients also received a glucose infusion test (GIT) using a total of 1.75 g/kg i.v. On IVGTT, 27 patients had a normal and 6 had a pathological glucose decay constant (k-value). On OGTT, 12 patients had an impaired glucose tolerance (IGT) and 3 patients were diabetic according to WHO standard, and only 18 patients had a normal glucose tolerance. While there was good correlation between both glucose and insulin concentrations between IVGTT and OGTT, only when reapplying the WHO criteria of a glucose concentration below 6.7 mmol/l to the concentration measured 180 minutes instead of 120 minutes after oral glucose load, the agreement between the two tests improved. The proportion of normal findings on GIT when compared to OGTT was identical. When using the appropriate definitions for normal and abnormal carbohydrate tolerance, interestingly the insulin (IRI) concentrations on OGTT were not discriminative between the normal and the pathological group, whereas IRI first phase secretion on IVGTT and IRI 0-180 AUC on GIT did discriminate. We conclude that the standard WHO OGTT criteria may have to be reconsidered in children with chronic renal failure and that OGTT should be extended to 180 minutes. The IVGTT, particularly when insulin early phase secretion (at 0, 1, 3 and 5 minutes) is also monitored, provides a reliable test for assessing glucose tolerance in children with chronic renal failure.