GLOMERULAR HYPERFILTRATION INCREASES THE RISK OF DEVELOPING MICROALBUMINURIA IN DIABETIC CHILDREN

An elevated glomerular filtration rate (GFR) is frequently detectable in type 1 diabetic children and adolescents and in those without any other evidence of incipient diabetic nephropathy. In 1982 we detected 23 patients with hyperfiltration (GFR >140 ml/min per 1.73 m(2)), aged 9-15 years, with diabetes for longer than 4 years; 23 age- and sex-matched patients with diabetes of a similar duration and without hyperfiltration served as controls. Both groups were followed until March 1992, by assessing GFR every 12 months, albumin excretion rate every 6 months, blood pressure and glycated haemoglobin (HbA1) every 3 months. Dietary protein intake was similar in patients with hyperfiltration and in controls. No other drug except insulin was used throughout the study. The insulin regimen was similar in the two groups. There was no significant difference between the two groups regarding albumin excretion, blood pressure and HbA1 at the beginning of the study. Of the 23 patients with hyperfiltration, 7 developed persistent microalbuminuria (defined as an overnight albumin excretion rate >30 mu g/min per 1.73 m(2) on at least 5 consecutive measurements); 2 of these patients had overt proteinura. Only 1 of the diabetics with normal GFR developed persistent microalbuminuria. The positive predictive value for microalbuminuria of an initial GFR >140 ml/min per 1.73 m(2) was 63%; the negative predictive value of an initial GFR <140 ml/min per 1.73 m(2) was 94%. The increase of albumin excretion rate into the microalbuminuric range precedes the elevation of both systolic and diastolic blood pressure. Persistent glomerular hyperfiltration is a risk factor for the development of microalbuminuria and incipient nephropathy in type 1 diabetic children, adolescents and young adults.