**For Adults**
Below are the equations and GFR calculators
for adults. In adults, the best equation for estimating glomerular
filtration rate (GFR) from serum creatinine is the Modification of Diet
in Renal Disease (MDRD) Study equation.
The Original MDRD Study equation is for
laboratories that use creatinine methods that have NOT been calibrated
to be traceable to isotope dilution mass spectrometry (IDMS). The
IDMS-traceable MDRD Study equation is for laboratories that use
creatinine methods that have been calibrated to be traceable to IDMS.
*Original MDRD Study Equation*
__Conventional units__
GFR (mL/min/1.73 m^{2}) = **186** x (S_{cr})^{-1.154} x (Age)^{-0.203} x (0.742 if female) x (1.212 if African-American)
*SI units*
GFR (mL/min/1.73 m^{2}) = **186** x (S_{cr}/88.4)^{-1.154} x (Age)^{-0.203} x (0.742 if female) x (1.212 if African-American)
**NOTE: This equation should be used ***only* with those creatinine methods that *have not been calibrated* to be traceable to IDMS.
*IDMS-traceable MDRD Study Equation *
*Conventional units*
GFR (mL/min/1.73 m^{2}) = **175** x (S_{cr})^{-1.154} x (Age)^{-0.203} x (0.742 if female) x (1.212 if African American)
*SI units*
GFR (mL/min/1.73 m^{2}) = **175** x (S_{cr}/88.4)^{-1.154} x (Age)^{-0.203} x (0.742 if female) x (1.212 if African American)
**NOTE: This equation should be used ***only* with those creatinine methods that *have been calibrated* to be traceable to IDMS. **If
you do not know whether your laboratory uses a method that has been
calibrated to be traceable to IDMS, talk to your in vitro
diagnostics manufacturer representative.**
GFR calculators for adults can be found on
the Health Professionals section of this website.
**For Children**
Currently, the best equation for estimating glomerular filtration rate (GFR) from serum creatinine in children is the Schwartz equation. Note that estimated GFR calculated using the original Schwartz equation will be influenced by the change to creatinine assays that are traceable to an isotope dilution mass spectroscopy (IDMS) reference measurement procedure. In general, IDMS-traceable creatinine methods will produce lower results, which, when used in the equation, will overestimate GFR. The overestimation may be as much as 20% to 40%. Thus, the estimated GFR may not accurately reflect the patient's kidney function.
*Please note the following important information*:
- Research to support a revised children's equation has been accepted for publication (Schwartz GJ, et al. Formulas to estimate GFR in children with chronic kidney disease.
*J Am Soc Nephrol*. 2008, in press). The new equations were based on an enzymatic creatinine method that had calibration traceable to an isotope dilution mass spectroscopy (IDMS) reference-measurement procedure. One of the new equations was based on serum creatinine, height, and age and is referred to as the interim Schwartz equation. **The interim Schwartz equation is intended only for enzymatic creatinine methods with calibration traceable to IDMS.** Laboratory personnel and physicians can estimate GFR for children by using this interim equation.
- Note that the interim Schwartz equation has not been validated for use with alkaline picrate ("Jaffe") creatinine methods. At this time, it is recommended not to estimate GFR for children when using an alkaline picrate ("Jaffe") method that has calibration traceable to IDMS. Further information is available.
Please check this website regularly or **sign up for our eUpdates** so that NKDEP can inform you of progress to introduce other formulas for estimating GFR in children. Subscribe to the Laboratory Professionals eUpdates here. |