An analogous estimate would be the estimated date of confinement for a pregnant woman based on her last menstrual period. However, the actual GFRs of those individuals will be distributed around that eGFR. Both equations were derived from large population studies and will generate an estimate of the mean GFR in a population of patients with the same age, gender, race, and serum creatinine. GFR LimitationsĮstimated glomerular filtration rate (eGFR) calculated using either the MDRD Study equation or the CKD-EPI equation is an estimate of GFR, not the actual GFR. However, the influence of imprecision of creatinine assays on the uncertainty of an eGFR value is greater at higher eGFR values and should be considered when assessing eGFR values > 60 mL/min/1.73 m 2. Direct comparison of the MDRD and CKD-EPI equations to the Cockcroft-Gault equation and to creatinine clearance measured from 24-hour urine collections has demonstrated their improved accuracy.Ī laboratory that reports eGFR numeric values > 60 mL/min/1.73 m 2 should use the CKD-EPI equation, because the CKD-EPI equation is more accurate for values > 60 mL/min/1.73 m 2 than is the MDRD Study equation. The MDRD Study and CKD-EPI equations are superior to traditional methods of approximating GFR.Both equations have been validated extensively in Caucasian and African American populations with impaired kidney function (eGFR 60 mL/min/1.73 m 2 compared to the MDRD Study equation however, the influence of imprecision of creatinine assays on the uncertainty of an eGFR value is greater at higher eGFR values and should be considered when assessing eGFRs > 60 mL/min/1.73 m 2. The MDRD Study and CKD-EPI equations are the most widely used and thoroughly validated equations.Because the MDRD and CKD-EPI equations employ age, gender, and race, providers may observe that CKD is present despite a serum creatinine concentration that appears to fall within or just above the normal reference range. The normal serum creatinine reference range does not necessarily reflect a normal GFR for a patient.Both the MDRD Study and CKD-EPI equations include variables to account for serum creatinine variation with age, gender, and race. Age, gender, and race all affect muscle mass and, in turn, serum creatinine. GFR is related inversely and nonlinearly to serum creatinine. GFR is poorly inferred from serum creatinine alone.NIDDK also encourages clinical laboratories to routinely estimate GFR and report the value when serum creatinine is measured for patients 18 and older, when appropriate and feasible. Reasons for Using the MDRD Study or CKD-EPI Equation to Estimate GFRīecause mild and moderate kidney injury is poorly inferred from serum creatinine alone, NIDDK strongly recommends the use of either the MDRD Study or CKD-EPI equation to estimate GFR from serum creatinine in adults. Patients under the age of 18: Calculate eGFR using the Schwartz equation for patients under age 18.Ĭaution: It is important to know the method used to measure creatinine in a blood, serum, or plasma sample, as it will affect the formula for estimating GFR in children.ĭetermine which calculator to use. eGFR should be used with caution in acutely ill or hospitalized patients who may exhibit rapidly changing kidney function.Īdults: Use either the Modification of Diet in Renal Disease (MDRD) Study equation or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Use of any serum creatinine-based estimate requires that kidney function be at a steady state. Calculate estimated GFR (eGFR) from serum creatinine levels to assess kidney function.
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