Renal Function in Relation to Metabolic Control in Children With Diabetes of Different Duration

To evaluate the interpretation of different kidney function tests in diabetic children and teenagers we have studied 47 children with a duration of diabetes up to 5 years, 61 children with a duration of 5.1‐10 years and 49 children with a duration of >10 years. Glomerular filtration rate (GFR) measuerd as inulin clearance or creatinine clearance, clearance PAH (C PAH ), filtration fraction (FF), 24‐hour urinary excretion of β 2 ‐microglobulin and albumin were examined and correlated with short‐ and longterm indices of metabolic control. In all groups of duration GFR as measured by inulin clearance was increased compared with reference values from age matched controls. In patients who had had diabetes for 0‐5 years a significant positive correlation was found between inulin clearance and blood glucose during the examination. Inulin clearance was also correlated to HBA 1c as well as to 24‐hour urinary glucose (mean of 4‐6 samples during two years). No such correlation was found in the group who had had diabetes for 5‐10 years but in patients with a duration of diabetes >10 years a significant inverse relation was found between GFR and HbA 1c . The 24‐hour urinary excretion of albumin was significantly higher in all groups of diabetics compared with controls. The urinary excretion of β 2 ‐microglobulin was similar in diabetics and controls. In the total material no significant correlation could be found between inulin clearance and creatinine clearance. On the other hand significant inverse correlations were found between creatinine clearance and indices of metabolic control. It is concluded that GFR as measured by inulin clearance is related to indices of metabolic control in a different way with different duration of diabetes. As long as the relation between the increased GFR detectable early in the disease to diabetic nephropathy is unknown the predictable value of this kidney function test is low and prospective studies are necessary. Creatinine clearancee assayed by the method of Jaffé is a poor indicator of GFR in diabetics with a poor metabolic control. 24‐hour urinary excretion of albumin measured by sensitive techniques might be predictive for diabetic nephropathy.