How the GFR Calculator can help you determine CKD

gfr calculator

Chronic kidney disease (CKD) is a serious health issue that affects millions of people worldwide. If you’re one of the millions of people living with CKD, it’s important to understand how the GFR calculator can help you determine your stage of renal impairment and prognosis. Keep reading to learn more about what the GFR calculator can do for you!

What Is The GFR Calculator?

The GFR calculator is a simple, online tool that uses your age, race, and creatinine level to estimate your glomerular filtration rate (GFR). This number is important because it helps doctors determine how well your kidneys are functioning. A normal GFR is around 100 mL/min, but if your GFR is lower than 60 mL/min, it’s an indication that you have CKD.

How Does The GFR Calculator Work?

The GFR calculator works by using your age, race, and creatinine level to estimate your glomerular filtration rate. To use the calculator, simply enter your age, race, and creatinine level into the fields provided. Once you’ve entered this information, the calculator will give you an estimated GFR.

Why Is The GFR Calculator Important?

The GFR calculator is important because it can help you determine your stage of CKD and prognosis. If your GFR is lower than 60 mL/min, it’s an indication that you have CKD. The earlier CKD is detected, the better the chances are of slowing or stopping its progression. That’s why the GFR calculator is such an important tool.

IDMS Traceable MRD Study Equation:

If you’re interested in learning more about the GFR calculator, you may want to check out the IDMS traceable MRD study equation. This equation is used to estimate GFR in adults and children. To use the equation, simply enter your age, race, and serum creatinine into the fields provided. Once you’ve entered this information, the calculator will give you an estimated GFR.

The CKD-EPI formula

Black female

If SCr

GFR = 166 × (SCr/0.7)-0.329 × 0.993age

If SCr > 0.7

GFR = 166 × (SCr/0.7)-1.209 × 0.993age

Black male

If SCr

GFR = 163 × (SCr/0.9)-0.411 × 0.993age

If SCr > 0.9

GFR = 166 × (SCr/0.9)-1.209 × 0.993age

Non-black female

If SCr

GFR = 144 × (SCr/0.7)-0.329 × 0.993age

If SCr > 0.7

GFR = 144 × (SCr/0.7)-1.209 × 0.993age

Non-black male

If SCr

GFR = 141 × (SCr/0.9)-0.411 × 0.993age

If SCr > 0.9

GFR = 141 × (SCr/0.9)-1.209 × 0.993age

The Mayo Quadratic Formula

If SCrCr

Estimated GFR for children using Schwartz formula

GFR (ml/min/1.73 m2) = k × height (cm) ÷ serum creatinine (mg/dL), where k is 0.413 for girls and 0.455 for boys

For children younger than 18 years of age with normal renal function, the following formulas can be used to estimate GFR:

For girls: GFR (ml/min/1.73 m2) = 0.413 × height (cm) ÷ serum creatinine (mg/dL)

For boys: GFR (ml/min/1.73 m2) = 0.455 × height (cm) ÷ serum creatinine (mg/dL)

The CKD-EPI Cystatin C equation

If CysCys

Where:

eGFRcysCys = Estimated Glomerular Filtration Rate from serum cystatin C levels

cystatin C = Serum cystatin C level (mg/L)

age = Patient’s age (years)

gender = Patient’s gender (male = 1, female = 0)

race = Patient’s race (black = 1, non-black = 0)

The MDRD Study equation

If SCrCr

GFR (ml/min/1.73 m2) = 186 × (serum creatinine/88.4)-1.154 × (age)−0.203 × (0.742 if female) × (1.212 if black)

The CKD-EPI Creatinine Equation

If SCrCr

Where:

eGFRcr = Estimated Glomerular Filtration Rate from serum creatinine levels

creatinine = Serum creatinine level (mg/dL)

age = Patient’s age (years)

gender = Patient’s gender (male = 1, female = 0)

race = Patient’s race (black = 1, non-black = 0)

The Modification of Diet in Renal Disease Study equation

If SCrCr

GFR (ml/min/1.73 m2) = 175 × (serum creatinine/88.4)-1.154 × (age)−0.203 × (0.742 if female) × (1.212 if black)

The Cockcroft-Gault equation

If SCrCr

Where:

CG = Cockcroft-Gault creatinine clearance (mL/min)

SCR = Serum creatinine level (mg/dL)

Age = Patient’s age (years)

Weight = Patient’s weight (kg)

Gender = Patient’s gender (male = 1, female = 0)

The Bedside estimation of the GFR equation

If SCrCr

Where:

eGFRbw = Estimated Glomerular Filtration Rate from body weight

SCR = Serum creatinine level (mg/dL)

Weight = Patient’s weight (kg)

height = Patient’s height (cm)

The Kidney Disease Outcomes Quality Initiative (KDOQI) equation

If SCrCr

Where:

eGFRkdoqi = Estimated Glomerular Filtration Rate from serum creatinine levels using the KDOQI equation

SCR = Serum creatinine level (mg/dL)

Age = Patient’s age (years)

Gender = Patient’s gender (male = 1, female = 0)

The Four variable MDRD equation

If SCrCr

GFR (ml/min/1.73 m2) = 175 × (serum creatinine/88.4)-1.154 × (age)−0.203 × (0.742 if female) × (1.212 if black)

The six-variable MDRD equation

If SCrCr

GFR (ml/min/1.73 m2) = 186.3 × (serum creatinine/88.4)-1.154 × (age)−0.203 × (0.742 if female) × (1.212 if black)

The CKD-EPI cystatin C equation for children and adolescents

If Cys Cys

Where:

eGFRcysCys = Estimated Glomerular Filtration Rate from serum cystatin C levels

cystatin C = Serum cystatin C level (mg/L)

age = Patient’s age (years)

gender = Patient’s gender (male = 1, female = 0)

race = Patient’s race (black = 1, non-black = 0)

How To Compare Serum Creatinine Level To GFR

The most common way to compare the serum creatinine level with GFR is by using the Cockcroft-Gault equation. This equation is used to estimate creatinine clearance, which is a measure of the kidney’s ability to filter out creatinine from the blood. The equation takes into account a person’s weight, height, gender, and age.

To use the Cockcroft-Gault equation, you will need to know your serum creatinine level and your weight in kilograms. You can then use the following formula to calculate your creatinine clearance:

Creatinine Clearance (mL/min) = (Weight in kg) x (Serum Creatinine Level in mg/dL) / (72 x Age in years)

For example, let’s say you are a woman who is 60 years old and weighs 70 kg. Your serum creatinine level is 1.2 mg/dL. Using the Cockcroft-Gault equation, your creatinine clearance would be:

Creatinine Clearance (mL/min) = (70 kg) x (1.2 mg/dL) / (72 x 60 years)

= 60 mL/min

Now let’s say you are a man who is 70 years old and weighs 80 kg. Your serum creatinine level is 1.4 mg/dL. Using the Cockcroft-Gault equation, your creatinine clearance would be:

Creatinine Clearance (mL/min) = (80 kg) x (1.4 mg/dL) / (72 x 70 years)

= 53 mL/min

As you can see, the man in this example has a lower creatinine clearance even though his serum creatinine level is higher. This is because the Cockcroft-Gault equation takes into account factors such as weight and age, which can affect the kidneys’ ability to filter out creatinine.

The Cockcroft-Gault equation is not perfect, however, and it can overestimate creatinine clearance in people who are very muscular or obese. In these cases, another equation called the Modification of Diet in Renal Disease (MDRD) Study equation may be more accurate.

The MDRD Study equation takes into account a person’s age, race, and gender as well as their serum creatinine level. It can be used to estimate GFR, which is a measure of kidney function. The following formula is used to calculate GFR from serum creatinine levels:

GFR (mL/min/1.73 m2) = 186.3 x (serum creatinine level in mg/dL)-1.154 x (age in years)-0.203 x (0.742 if female) x (1.212 if black)

For example, let’s say you are a woman who is 60 years old and your serum creatinine level is 1.2 mg/dL. Using the MDRD Study equation, your GFR would be:

GFR (mL/min/1.73 m2) = 186.3 x (1.2 mg/dL)-1.154 x (60 years)-0.203 x (0.742)

= 60 mL/min/1.73 m2

Now let’s say you are a man who is 70 years old and your serum creatinine level is 1.4 mg/dL. Using the MDRD Study equation, your GFR would be:

GFR (mL/min/1.73 m2) = 186.3 x (1.4 mg/dL)-1.154 x (70 years)-0.203 x (1)

= 53 mL/min/1.73 m2

As you can see, the GFR estimated by the MDRD Study equation is lower in the man even though his serum creatinine level is higher. This is because the MDRD Study equation takes into account a person’s age, race, and gender as well as their serum creatinine level.

The Bottom Line

The GFR calculator is a simple, online tool that can help you determine your stage of CKD and prognosis. If your GFR is lower than 60 mL/min, it’s an indication that you have CKD. The earlier CKD is detected, the better the chances are of slowing or stopping its progression. That’s why the GFR calculator is such an important tool.

Disclaimer:

If you’re interested in learning more about CKD and the GFR calculator, be sure to talk to your doctor. They can give you more information about CKD and how to manage it.

References

1. Estimated Glomerular Filtration Rate (eGFR), National Kidney Foundation.https://www.kidney.org/atoz/content/gfr

2. Measurement of renal function in patients with chronic kidney disease, British Journal of Clinical Pharmacology, US National Library of Medicine, National Institutes of Health.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791974/

3. Creatinine blood test, Medline Plus, US National Library of Medicine, National Institutes of Health.https://medlineplus.gov/ency/article/003475.htm

4. Creatinine (Blood), University of Rochester Medical Center.https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=167&ContentID=creatinine_serum

5. Recommendations for improving serum creatinine measurement: a report from the Laboratory Working Group of the National Kidney Disease Education Program. Clinical Chemistry, US National Library of Medicine, National Institutes of Health.https://www.ncbi.nlm.nih.gov/pubmed/16332993

6. Chronic Renal Failure, StatPearls, US National Library of Medicine, National Institutes of Health.https://www.ncbi.nlm.nih.gov/books/NBK535404/

7. Renal function in diabetic nephropathy, World Journal of Diabetes, US National Library of Medicine, National Institutes of Health.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3083882/

8. Drinking more water does not slow the decline of kidney function for kidney disease patients, EurekAlert.https://www.eurekalert.org/pub_releases/2018-05/lhri-dmw050818.php

 

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