eGFR Test
Renal function test is an indication of the kidney's condition and its role in renal physiology. Glomerular filtration rate is a measure of kidney function.
An estimated glomerular filtration rate (eGFR) test is a blood test that is used to figure out how well a person’s kidneys are working. The test measures the concentration of creatinine in the blood (serum), then using a formula to mathematically derive an estimated rate of filtration, to know how effective the kidney functions in filtering.
This formula uses age, gender and the level of creatinine in the blood to estimate the GFR. Creatinine is a waste product made by the muscles. It is usually removed from the blood by the kidneys before passing out in the urine. When the kidneys are not working well, more creatinine stays in the blood. The doctor may also ask for other tests related to renal function, which inform the doctor to observe for other signs and conditions related to kidney function such as albumin in the urine (albuminuria), blood in the urine (hematuria), high blood pressure and diabetes. Albumin is a protein that is normally found in blood, however properly functioning kidneys do not allow it to get into the urine. However, damaged ones do. So, if the results of this test show that there's albumin in the urine, there is a high chance of kidney disease. A urinalysis may also be ordered to help the doctor to check for any signs of kidney damage in the urine.
Purpose of test
Our doctors will order an eGFR test if he suspects chronic kidney disease. The doctor may order an eGFR test if a patient complains of these symptoms:
- Dry and persistently itchy skin
- Muscle cramps
- Sleep problems
- Foamy or bloody urine
- Nausea and vomiting
- Concentration problems
- Swollen ankles and feet
- High blood pressure
- Increase in frequency of urination
- Fatigue and low energy levels
- Poor appetite
The early stages of kidney disease normally do not cause symptoms, therefore if one has any pre-existing condition like diabetes, high blood pressure and cardiovascular disease (all of which can affect the kidneys). The doctor will most likely order for this test at regular intervals, also if a patient have a family history of kidney disease, this test will be ordered.
If a patient has already been diagnosed with kidney disease, our doctors will still order an eGFR test regularly to monitor how well one’s kidneys are faring as patient undergoes treatment.
The main function of the kidneys is to clean the blood by filtering out waste. The glomeruli (tiny filters found in the kidneys) are central to this function. Therefore, the eGFR rate is how much blood these glomeruli filter per minute, and it works by measuring the levels of creatinine in the blood.
Creatinine is one of the types of waste that the kidneys help to filter out of the body. Therefore, if a high level of creatinine is found in the blood, it might signal that a person’s kidneys (the glomeruli, in particular) are not doing a good job of filtering and cleaning out a person’s blood.
>Limitations
One should also note that an eGFR test result can be influenced by many factors.
Therefore, an
eGFR test result may not be accurate if a patient is:
- Pregnant
- Under the age of 18
- Elderly (because GFR normally declines with age)
- On a vegetarian diet
- Significantly more or less muscular than the average person
Accordingly, the doctor will check if any applies to the patient before making a diagnosis of chronic kidney disease or ordering further tests to confirm the diagnosis.
An eGFR test is cannot solely be used to check for kidney disease, it is usually requested alongside a urine test for albumin to diagnose kidney disease. Though the eGFR is a good test, it is not right for everyone. For example, this test may not be accurate for people who are younger than 18years of age, pregnant, overweight or very muscular.
Though the eGFR test is not 100 percent accurate, it can give an estimate of filtration rate.
>Before the test
The patient is expected to discuss all symptoms, as well as family history of kidney disease (if any) with the doctor
Patients should disclose all medical conditions and the medications they are taking to their doctors. This is because certain drugs can interfere with eGFR results by increasing creatinine levels.
Disclose if one is pregnant or if there is any chance of pregnancy, as this can affect the test results.
How the test is done
A sterile syringe will be inserted into the vein in the arm and the blood will be drawn. One may feel a moderate amount of pain or merely a sting, and the entire process will probably take under a minute to complete.
Interpreting results
The eGFR result will be a number and this is what each range of numbers means:
- GFR 90 and above: the patient has normal to high kidney function.
- GFR 60–89: There is a mild reduction of kidney function. This does not mean kidney disease. It is only when there are other signs of kidney damage that this GFR number may signify kidney disease.
- GFR 45–59: There is a mild to moderate reduction in kidney function, and it may signify kidney disease.
- GFR 30–44: This shows that there is a moderate to severe reduction of kidney function.
- GFR 15–29: This signifies a severe reduction of kidney function.
- GFR 15 or less: This signifies kidney failure and the patient will need to be on dialysis or get a kidney transplant.
It is only a doctor that can give the most accurate interpretation of results based on the eGFR result and other individual symptoms, complications, and medical history.
