In the text below the tool you can find more information about the possible GFR formulas.
The GFR calculator estimates the glomerular filtration rate, which is an overall index of kidney function, both for adult and pediatric patients.
It offers results from three different equations and is based on serum creatinine levels in mg/dL, patient age, gender and race.
This calculator uses the following formulas (click on each of the links provided to jump to it):
■ The IDMS-traceable MDRD equation;
■ The CKD-EPI formula;
■ The Mayo Quadratic formula;
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Glomerular filtration rate explained
GFR is the most important of the parameters that evaluate kidney function. It is estimated through different methods based on serum creatinine.
Creatinine is the break down product of the creatinine phosphate, involved in muscular function. Serum creatinine levels determine the clearance that is used further on to establish GFR.
GFR offers information on the amount of liquid that gets filtered by the capillaries of the kidney glomerular into the Bowman's capsule during a specific time period.
Thus, its value shows how efficiently the kidneys perform their function, that of cleaning blood of different waste products and toxins and their excretion through urine.
Glomerular filtration rate can be physically determined by comparing concentrations of a marker substance in a sample of blood an in a sample of urine.
The above calculator employs the following formulas to determine the glomerular filtration rate:
The IDMS-traceable MDRD equation:
GFR = 175 x (SCr)-1.154 x (Age)-0.203 x (0.742 only if female) x (1.212 only if black)
The CKD-EPI formula is composed based on patient gender and race, as presented in the following table:
|Race||Gender||Serum Creatinine (SCr)||Formula (GFR = …)|
|White/ Other race||Female||≤0.7||144 x (SCr/0.7)-0.329 x 0.993Age|
|>0.7||144 x (SCr/0.7)-1.209 x 0.993Age|
|Male||≤0.9||141 x (SCr/0.9)-0.411 x 0.993Age|
|>0.9||141 x (SCr/0.9)-1.209 x 0.993Age|
|Black||Female||≤0.7||166 x (SCr/0.7)-0.329 x 0.993Age|
|>0.7||166 x (SCr/0.7)-1.209 x 0.993Age|
|Male||≤0.9||163 x (SCr/0.9)-0.411 x 0.993Age|
|>0.9||163 x (SCr/0.9)-1.209 x 0.993Age|
The Mayo Quadratic formula:
GFR = e(1.911 + 5.249/SCr - 2.114/SCr2 - 0.00686 x Age - (0.205 only if Female))
e = 2.71828182845905
SCr = the serum creatinine, either expressed in mg/dL. When SCr is expressed in mol/L, the conversion rate that should be used is 88.4 mol/L = 1 mg/dL.
Note that in any case serum creatinine is less than 0.8 mg/dL, the Mayo Quadratic Formula uses 0.8 mg/dL default for SCr.
In the case of pediatric patients, the Schwartz formula is used:
GFR = 0.41 x Height (in cm) / SCr
The optimal GFR level is around 60 mL/min/1.73 m2 level. The table below summarises the chronic kidney disease stages and their associated glomerular filtration rates:
|CKD stage||GFR level (mL/min/1.73 m2)||Other observations|
|0 Stage - Normal kidney function||≥90||No proteinuria|
|1st Stage||≥90||Kidney damage signs|
|2nd Stage||60 – 89||Mild|
|3rd Stage||30 – 59||Moderate|
|4th Stage||15 – 29||Severe|
|5th Stage||<15||Kidney Failure|
1. Guyton, Arthur; Hall, John (2006) Chapter 26: Urine Formation by the Kidneys: I. Glomerular Filtration, Renal Blood Flow, and Their Control. In Gruliow, Rebecca. Textbook of Medical Physiology (Book) (11th ed.) Philadelphia, Pennsylvania: Elsevier Inc.
2. Mathew TH, Johnson DW, Jones GR. Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: revised recommendations. The Medical Journal of Australia. 2007; 187 (8): 459–63.
3. Jin R, Grunkemeier GL, Brown JR, Furnary AP. Estimated glomerular filtration rate and renal function. Ann Thorac Surg. 2008; 86(1):1-3.
4. Kampmann JP, Hansen JM. Glomerular filtration rate and creatinine clearance. Br J Clin Pharmacol. 1981; 12(1): 7–14.
No. Of Variables: 4
Published On: July 2, 2017 · 08:01 AM
Last Checked: July 2, 2017
Next Review: July 2, 2023