[Comparison of methods for evaluating renal function (Data of Kaunas University of Medicine Hospital in 2006)]

Abstract

Cockcroft-Gault formula and Modification of Diet in Renal Disease (MDRD) equation are widely used as indirect estimates of renal function. The precision and reliability of these formulas regarding kidney function are still discussed. The aim of our study was to evaluate glomerular filtration rate by different methods and compare the results. Data on patients in whom renal function was evaluated at the Clinic of Nephrology of Kaunas University of Medicine Hospital in 2006 are presented in this article. Glomerular filtration rate was assessed based on 24-hour endogenous creatinine clearance and calculated using three formulas: Cockcroft-Gault, abbreviated MDRD, and complete MDRD. Blood serum creatinine level was measured by the standardized Jaffe assay. Glomerular filtration rate was examined in 125 patients. Their mean age was 58.07+/-18.962 years. The mean endogenous creatinine clearance was 31.1287+/-31.14 783 mL/min. The mean glomerular filtration rate calculated by Cockcroft-Gault formula was 34.1220+/-29.02 967 mL/min, by abbreviated MDRD formula was 29.8212+/-25.83 866 mL/min/1.73 m2, and by complete MDRD formula was 28.6884+/-24.99 353 mL/min/1.73 m2. There was no statistically significant difference in mean glomerular filtration rates estimated using all methods in the evaluation of kidney function. When the reliability of formulas was analyzed depending on each stage of chronic kidney disease, it was found that Cockcroft-Gault and MDRD formulas, in contrast to endogenous creatinine clearance, did not precisely reflect kidney function in stages 1 and 2 of chronic kidney disease. Estimates by Cockcroft-Gault and MDRD formulas correctly showed decreased kidney function in stages 3 and 4 of chronic kidney disease. Formulas were not reliable, in contrast to endogenous creatinine clearance, when patients were in end-stage chronic kidney disease. CONCLUSIONS. Cockcroft-Gault and MDRD formulas are best for the evaluation of moderate degree of renal insufficiency, and in early stage of chronic kidney disease, underestimation of glomerular filtration rate is possible by using formulas. Estimates of glomerular filtration rate based on formulas are higher as compared to endogenous creatinine clearance measurements in end-stage chronic kidney disease.