To assess, in diabetic nephropathy, the accuracy of a method that estimates glomerular function with age, body weight, and serum creatinine as parameters.
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).
For GFR measurements <100 ml · min−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 <0.0001). The slope of this regression line did not differ significantly from identity or the 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).
This formula, corrected for body surface area, gives accurate estimates of GFR when GFR <100 ml·min−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.
