Glomerular Filtration Rate (GFR)
The kidneys remove excess fluid and waste materials by a filtration process known as Glomerular filtration. It is a calculation that determines the efficiency of the filtration process, thus helping measure kidney functioning and to determine the stage of the chronic kidney disease. The calculation of GFR is done by a mathematical formula that compares an individual’s age, sex, race, and size to serum creatinine levels.
Why is the test required?
A person may require the GFR test if a physician notices any signs and symptoms of kidney disease. The test may also be recommended to determine the progression of kidney disease and to determine the risk of contracting kidney disease owing to high blood pressure, heart disease, diabetes, urinary tract infections, or urinary blockage.
When is the test ordered?
The test may be ordered if a kidney disease is suspected and if the patient shows the following signs and symptoms:
- High blood pressure
- Swelling around eyes
- Muscle cramps
- Change in the frequency of urination
- Decrease in the amount of urine
- Dark urine
- Mid back pain
- Problems urinating
- Burning sensation during urination
- Swelling in the face, around eyes, ankles, wrists and abdomen.
How is the sample collected?
A blood sample is collected from a vein in the arm.
How to prepare for the test?
To calculate GFR, blood creatinine levels are measured. Therefore, overnight fasting is recommended and the person taking the test may be asked to avoid eating cooked meat as it might elevate creatinine levels temporarily.