Estimated glomerular filtration rate (eGFR): Introduction, Test Result, Normal Range, Unit, Test Methods, Clinical Significance, and Keynotes

Introduction of Estimated glomerular filtration rate (eGFR)

The estimated glomerular filtration rate (eGFR) is an indicator that helps to know how well your kidneys are functioning. It is an estimated value based on a blood test and age, sex, and body type.

Estimated glomerular filtration rate (eGFR)-Test Result, Normal Range, Unit, and Test Methods

Clinical Significances of Estimated glomerular filtration rate (eGFR)

An eGFR test is clinically important in the following clinical features-

• Low and high urinating frequency
• Body itching
• Feeling tired
• Swelling in body parts like arms, legs, or feet
• Muscle cramps
• Nausea and vomiting
• Anorexia (loss of appetite)

See the table below for the average estimated eGFR based on age.

Age (years)	Average eGFR
20–29	116
30–39	107
40–49	99
50–59	93
60–69	85
70+	75

The stages of chronic kidney disease (CKD) and the role of eGFR –

Stage	eGFR	Kidney Function (%)	Description
1.	≥90	90-100	Possible kidney damage ( e.g.proteinuria) with normal kidney function
2.	60-89	60-89	Kidney damage with mild loss of kidney working
3a	45-59	45-59	Mild to moderate loss of kidney function
3b	30-44	30-44	Moderate to a severe loss of kidney function
4.	15-29	15-29	Severe loss of kidney function
5.	< 15	<15	Kidney failure

Keynotes on eGFR

• A normal eGFR is 60 or more. If the eGFR is less than 60 for 3 months or more, the kidneys may not be working properly.
• Other than the eGFR test, an ultrasound or a renal biopsy may be ordered to find the cause of renal/kidney disease.
• eGFR may still be in the normal range even if somebody has some signs of kidney damage, such as protein in their urine or physical damage to their kidneys.
• In estimated GFR (eGFR), normally creatinine and additionally cystatin C are tested whereas in measured GFR (mGFR) inulin (a kind of fiber that is found in some plant foods) and iohexol (contrast agent used in imaging tests) are tested.
• Risk factors of chronic kidney disease (CKD) are diabetes, high blood pressure (BP), obesity/overweight, aging, and a family history of kidney failure or CKD.

Some tips that keep kidneys healthy are

1. Maintain blood pressure (normally less than 120/80).
2. Control blood sugar (in case of diabetes).
3. Follow taking a low-salt and low-saturated-fat diet.
4. Take yourself active for at least half an hour most days of the week either walking or biking.
5. Keep your biomass index (BMI) balanced and leave smoking or using tobacco if you are in the habit.

• MDRD stands for Modification of Diet in Renal Disease.

Further Reading

1. https://www.kidney.org/atoz/content/gfr
2. https://www.kidneyfund.org/all-about-kidneys/tests/blood-test-egfr
3. https://www.kidneyfund.org/all-about-kidneys/tests/egfr/egfr-test-change-removal-race-calculation
4. https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/kidney-disease/laboratory-evaluation/glomerular-filtration-rate/estimating