The National Kidney Foundation has advocated the use of the abbreviated Modification of Diet in Renal Disease (MDRD) equation to estimate glomerular filtration rate (GFR) from serum creatinine measurements in clinical laboratories. However, healthy persons were not included in the development of the MDRD equation...Conclusion: The MDRD equation systematically underestimates GFR in healthy persons. A new equation developed with patients who have chronic kidney disease and healthy persons may be a step toward accurately estimating GFR when the diagnosis of chronic kidney disease is unknown