Prediction of glomerular filtration rate from serum creatinine concentration in advanced chronic renal failure

Prediction of glomerular filtration rate from serum creatinine concentration in advanced chronic renal failure. In 85 patients with established chronic renal failure, as manifested by serum creatinine concentration ([Cr]) > 0.177 mM (> 2 mg/dl), urinary clearance of 99mTc-DTPA (GFR) and [Cr] were determined one to four times and averaged. GFR was expressed per 3 m2 of height2 rather than in terms of 1.73 m2 of surface area because weight changes but height does not. GFR in these patients averaged 13 ml/min/3 m2 (range 2 to 37). The following equations were derived for predicting GFR from [Cr]-1 (mM-1), age (years) and weight (kg): males, GFR = 7.57 [Cr]-1 - 0.103 age + 0.096 weight - 6.66; females, GFR = 6.05 [Cr]-1 - 0.08 age + 0.08 weight - 4.81. These equations predict GFR in this series with a root mean square error of 3.0 ml/min and account for 89% of the observed variation in GFR. They are applicable only to patients with [Cr] > 0.177 mM (2 mg/dl). More precise estimates can be obtained by including a value for 24-hour urinary urea N, as a measure of protein intake. Less precise but simpler estimates can be obtained from [Cr]-1 alone: males, GFR = 7.58 [Cr]-1 - 4.29; females, GFR = 6.11 [Cr]-1 - 3.8. Expressing [Cr] in mg/dl, the latter equations become: males, GFR = 86 [Cr]-1 - 4.29; females, GFR = 69 [Cr]-1 - 3.8.