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

formula

These values were then corrected for body surface area (1.73 m2).

Results

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).

Conclusions

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.

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