Estimating glomerular filtration rate with a modification of diet in renal disease equation: Implications for pharmacy

Abstract

Chronic kidney disease (CKD) is a major health concern world-wide. The number of patients in the United States requiring dialysis or kidney transplantation is projected to increase to 651,000 by 2010.1 In spite of this increase, CKD remains underdiagnosed and thus under-treated due to a lack of agreement on the definition of this disorder, as well as disagreement on the classification of stages in the progression of CKD. In addition, there is no uniform application of simple tests for detecting and evaluating CKD. In 2002, the National Kidney Foundation (NKF) revised its practice guidelines for CKD and now recommends the use of a four-variable modification of diet in renal disease (MDRD) equation (MDRD4 equation) or the Cockcroft–Gault equation for creatinine clearance (CLcr) to estimate the glomerular filtration rate (GFR) and better detect early-onset CKD.1,2 These guidelines further recommend that clinical laboratories estimate the GFR using an equation designed to estimate or predict the GFR based on available patient data, such as age, sex, weight, and serum creatinine, whenever reporting a serum creatinine measurement. This first recommendation has led to some confusion about the applicability and utility of the MDRD 4 equation in drug-dosing adjustments for patients with renal impairment. This article reviews the evidence that has led to the NKF’s recommendations and their application to pharmacy and drug dosing.