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

There is debate about the most suitable test for investigation of glucose t olerance in children with chronic renal failure. We therefore studied the a greement between the two most commonly used glucose tolerance tests in 33 c hildren with chronic renal failure (mean age 10.9 +/- 5.3 years, median GFR was 24 ml/min/1.73 m(2)). All children underwent an oral glucose tolerance test (OGTT) with blood sampling up to 180 minutes and after an oral load o f 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 t o account for the differing glucose load, a subgroup of 19 patients also re ceived a glucose infusion test (GIT) using a total of 1.75 g.kg i.v. On IVG TT, 27 patients had a normal and 6 had a pathological glucose decay constan t (k-value). On OGTT, 12 patients had an impaired glucose tolerance (IGT) a nd 3 patients were diabetic according to WHO standard, and only 18 patients had a normal glucose tolerance. While there was good correlation between b oth glucose and insulin concentrations between IVGTT and OGTT, only when re applying the WHO criteria of a glucose concentration below 6.7 mmol/l to th e concentration measured 180 minutes instead of 120 minutes after oral gluc ose load, the agreement between the two tests improved. The proportion of n ormal findings on GIT when compared to OGTT was identical. When using the a ppropriate definitions for normal and abnormal carbohydrate tolerance, inte restingly the insulin (IRI) concentrations on OGTT were not discriminative between the normal and the pathological group, whereas IRI first phase secr etion 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 m inutes) is also monitored, provides a reliable test for assessing glucose t olerance in children with chronic renal failure.