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 o ther evidence of incipient diabetic nephropathy. In 1982 we detected 2 3 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-mat ched patients with diabetes of a similar duration and without hyperfil tration served as controls. Both groups were followed until March 1992 , by assessing GFR every 12 months, albumin excretion rate every 6 mon ths, blood pressure and glycated haemoglobin (HbA1) every 3 months. Di etary protein intake was similar in patients with hyperfiltration and in controls. No other drug except insulin was used throughout the stud y. The insulin regimen was similar in the two groups. There was no sig nificant difference between the two groups regarding albumin excretion , blood pressure and HbA1 at the beginning of the study. Of the 23 pat ients with hyperfiltration, 7 developed persistent microalbuminuria (d efined 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 ov ert proteinura. Only 1 of the diabetics with normal GFR developed pers istent microalbuminuria. The positive predictive value for microalbumi nuria of an initial GFR >140 ml/min per 1.73 m(2) was 63%; the negativ e 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 ran ge precedes the elevation of both systolic and diastolic blood pressur e. Persistent glomerular hyperfiltration is a risk factor for the deve lopment of microalbuminuria and incipient nephropathy in type 1 diabet ic children, adolescents and young adults.