Creatinine for estimation of glomerular filtration rate

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Abstract
The aim of this study was to evaluate the plasma creatinine concentration (PCr) and creatinine clearance (CCr) for estimation of glomerular filtration rate (GFR). Inulin clearance (Cin) was used as the reference standard for GFR. Thirty-nine concurrentCin andCCr studies provided data for comparingCin with the measuredCCr and with the calculatedCCr (calc-CCr). (Calc-CCr=k·L/PCr, where L=height in centimeters and k is the proportionality constant.) Thirty-one children 5.3–20.8 years of age, withCin ranging from 2.8 to 138.8 ml/min per 1.73 m2, participated in these studies at The Children's Mercy Hosptial. The measuredCCr was 16.7±10.3 ml/min per 1.73 m2 (PCin, and the calc-CCr overestimatedCin by a mean of 31.6±20.8 ml/min per 1.73 m2 (PCin andCCr (r=0.96), andCin and calc-CCr (r=0.90), the 95% confidence intervals are quite broad. Hence, theCCr and the calc-CCr, derived using Schwartz values for k, consistently overestimate GFR. However, if the k value in the equation GFR=k·L/PCr is derived from k=Cin/L, rather than from k=CCr·PCr/L, a more accurate estimate of GFR may be obtained.