Accurate Estimation of Glomerular Filtration Rate in Diabetic Nephropathy From Age, Body Weight, and Serum Creatinine

Abstract

Objective To assess, in diabetic nephropathy, the accuracy of a method that estimates glomerular function with age, body weight, and serum creatinine as parameters. Research Desihn and Methods Glomerular filtration rate (GFR) was measured 57 times in 20 subjects with insulin-dependent diabetes mellitus and nephropathy with a single injection of ⁵¹Cr-EDTA. At the same time, the estimated creatinine clearance (ml/min) was calculated with the Cockroft-Gault formula These values were then corrected for body surface area (1.73 m²). Results For GFR measurements −1 · 1.73 m⁻² (n = 41), there was a strong positive correlation with the estimated creatinine clearance corrected for body surface area (r = 0.94, P y-intercept from zero. On average, the Cockroft-Gault formula (corrected for body surface area) underestimated the GFR by only 3.1 ml·min⁻¹·1.73 m⁻² (9.7 SD). Conclusions This formula, corrected for body surface area, gives accurate estimates of GFR when GFR −1·1.73 m^–2. This formula could be used with an acceptable degree of confidence when repeated isotope assessments of renal function in diabetic nephropathy are impracticable.