Estimated Glomerular Filtration Rate (eGFR)

What is the use of this test?
The eGFR is used to monitor kidney status and to detect early kidney damage and . A creatinine test is
performed and estimated glomerular filtration rate is calculated. Your physician may order for a creatinine test if you already have chronic kidney disease(CKD). This test is also recommended for those with hypertension nd dialysis as these diseases may lead to kidney damage.

When is eGFR ordered?
The eGFR can be performed when we go for a creatinine test. This test will give early warning signs of kidney disease. The doctor will order this test for any of the following symptoms:
  • Swelling or puffiness, particularly around the eyes or in the face, wrists, abdomen, thighs, or ankles
  • Urine that is foamy, bloody, or coffee-colored
  • A decrease in the amount of urine
  • Problems urinating, such as a burning feeling or abnormal discharge during urination, or a change in the frequency of urination, especially at night
  • Mid-back pain (flank), below the ribs, near where the kidneys are located
  • High blood pressure (hypertension)
As kidney disease worsens, symptoms may include:
  • Urinating more or less often
  • Feeling itchy
  • Tiredness, loss of concentration
  • Loss of appetite, nausea and/or vomiting
  • Swelling and/or numbness in hands and feet
  • Darkened skin
  • Muscle cramps

What does the test result mean? Looking for reference ranges?

The eGFR helps to detect kidney disease in its early stages more reliably than the creatinine test alone. Because the calculation works best for estimating reduced kidney function, the National Kidney Foundation (NKF) suggests only reporting actual results once values are < 60 mL/min (they state normal values as 90-120 mL/min). An eGFR below 60 mL/min suggests that some kidney damage has occurred.

The NKF recommends that everyone "know their GFR number." A person's eGFR should be intepreted in relation to the person's clinical history and presenting conditions, utilizing the following table:

Kidney damage stage description gfr Other Findings
1 Normal or minimal kidney damage with normal GFR 90+ Protein or albumin in urine are high, cells or casts seen in urine
2 Mild decrease in GFR 60-89 Protein or albumin in urine are high, cells or casts seen in urine
3 Moderate decrease in GFR 30-59
4 Severe decrease in GFR 15-29
5 Kidney failure <15


Is there anything else I should know?

Another method of evaluating kidney function and potentially estimating GFR involves the measurement of the blood level of cystatin C. There is increasing interest in the use of this test for these purposes and several studies have been performed comparing calculations of eGFR using creatinine, cystatin C, or both. According to the National Kidney Foundation, two meta-analyses concluded that cystatin c is superior to creatinine as a marker of kidney function. The NKF also states that a formula for calculating eGFR that includes both blood creatinine and cystatin C values may improve that estimate.

The creatinine clearance test also provides an estimate of kidney function and of the actual GFR. However, in addition to the serum creatinine, this test requires a timed urine collection (24 hours) for urine creatinine measurement in order to compare blood and urine creatinine concentrations and to calculate the clearance.

The actual amount of creatinine that a person produces and excretes is affected by their muscle mass and by the amount of protein in their diet. Men tend to have higher creatinine levels than women and children.

A person's GFR decreases with age and some illnesses and can increase during pregnancy.

A slightly different equation should be used to calculate the eGFR for those under the age of 18. The eGFR equations are not valid for those who are 75 year of age or older because muscle mass normally decreases with age.

An eGFR may not be as useful for those who differ from normal creatinine concentrations. This may include people who have significantly more muscle (such as a body builder) or less muscle (such as a muscle-wasting disease) than the norm, those who are extremely obese, malnourished, follow a strict vegetarian diet, ingest little protein, or who take creatine dietary supplements.

The eGFR may also be affected by a variety of drugs, such as gentamicin, cisplatin, and cefoxitin that increase creatinine levels, and by any condition that decreases blood flow to the kidneys.

The calculation for eGFR is intended to be used when kidney function and creatinine production are stable. If a creatinine level is measured when the kidney function is changing rapidly, such as with acute kidney failure, then it will not give a useful estimate of the filtration rate.

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