The old and new methods of assessing kidney function.

Chronic kidney disease is a worldwide problem. Accurate assessment of kidney function is important for defining stages of kidney disease and assisting with drug dosing. Glomerular filtration rate (GFR) is a good index of the health of the kidney. Although measured GFR using an exogenous substance is the most accurate, it is difficult to obtain due to cost and resources. Equations calculating creatinine clearance and estimated GFR as a measure of kidney function have been developed using serum creatinine as a marker of kidney function. The Cockcroft-Gault, Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration equations have been shown to have statistically significant differences in estimating GFR in various populations. Drug-dosing adjustments based on the various equations may differ. However, without clinical outcome data, it is yet to be determined whether these differences are clinically significant.