Comparison of Measured Creatinine Clearance and Clearances Estimated by Cockcroft-Gault and MDRD Formulas in Patients with a Single Kidney

Abstract

There are doubts about whether the values obtained from the Cockroft-Gault (Cl CG ) and Modification of Diet in Renal Disease (GFR MDRD ) formulas are comparable to the more traditional formula used to obtain the creatinine clearance from a 24-hour urine collection (ClCr m ), particularly in patients with only one kidney. The present study aimed to compare these formulas in individuals with one remaining kidney after previous nephrectomy (Nx) and to verify which estimated formula correlates more closely with ClCr m . Thirty-six patients who had undergone Nx had their renal filtration analyzed with Cl CG , GFR MDRD and by ClCr m . The average time after Nx was years, and the average age at the time of the study was years old (X ± SD). The results of three clearances were mL·min·m 2 for ClCr m , mL·min·m 2 for ClCr CG , and mL·min·m 2 for GFR MDRD (with ClCr m > ClCr CG and GFR MDRD ; ). No difference was found between the ClCr CG and GFR MDRD values (). The data demonstrated that both estimate formulas were strongly correlated with ClCr m , although ClCr CG was more closely associated with ClCr m than GFR MDRD (ClCr CG with and GFR MDRD with ; ). In conclusion, for people with only one kidney remaining after NX, our data showed that glomerular filtration rate estimation by ClCr CG is more related to the values obtained with the traditional clearance measurement based on a 24-hour urine collection test.