Were you looking for Epidermal Growth Factor Receptor, also known as EGFR? If so, see the article on the EGFR test.
At a Glance
Why Get Tested?
To assess kidney function
When to Get Tested?
When your doctor thinks that you may have kidney damage or that you may be at risk for developing it
The eGFR is a calculated estimate of the actual glomerular filtration rate and is based on your serum creatinine concentration, which requires a blood sample from a vein in your arm; the recommended calculation uses a formula that also includes your age, gender, and race. Other formulas may also include height and weight.
Test Preparation Needed?
The Test Sample
What is being tested?
Glomerular filtration rate (GFR) is a measure of the function of the kidneys. Glomeruli are tiny filters in the kidneys that allow waste products to be removed from the blood, while preventing the loss of important constituents, including proteins and blood cells. Every day, healthy kidneys filter about 200 quarts of blood and produce about 2 quarts of urine. The glomerular filtration rate refers to the amount of blood that is filtered by the glomeruli per minute. When a person's kidney function declines due to damage or disease, then the filtration rate decreases and waste products begin to accumulate in the blood.
Chronic kidney disease (CKD) is associated with a decrease in kidney function that is often progressive. CKD can be seen with a variety of conditions, including diabetes and high blood pressure. Early detection of kidney dysfunction can help to minimize the damage. This is important as symptoms of kidney disease may not be noticeable until as much as 30 to 40% of kidney function is lost.
A measured GFR is considered the most accurate way to detect changes in kidney status, but measuring the GFR directly is complicated, requires experienced personnel, and is typically performed in a research setting. Because of this, an estimate – the eGFR – is usually used.
The eGFR is a calculation based on a serum creatinine test. Creatinine is a muscle waste product that is filtered from the blood by the kidneys and excreted into the urine at a relatively steady rate. When kidney function decreases, less creatinine is excreted and concentrations increase in the blood. With the creatinine test, a reasonable estimate of the actual GFR can be determined.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm; depending on the formula used, your age, gender, race, height, and weight may also be needed.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 311-312.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 438-439.
Patel, P. (Updated 2009 August 12). Glomerular filtration rate. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/007305.htm. Accessed October 2009.
(2009 February). The Kidneys and How They Work. National Kidney and Urologic Diseases Information Clearinghouse [On-line information]. Available online at http://kidney.niddk.nih.gov/kudiseases/pubs/yourkidneys/ through http://kidney.niddk.nih.gov. Accessed October 2009.
(Reviewed 2009 April 7). Laboratory Professionals, Estimating and Reporting GFR. National Kidney Disease Education Program [On-line information]. Available online at http://www.nkdep.nih.gov/labprofessionals/estimate_report_gfr.htm through http://www.nkdep.nih.gov. Accessed October 2009.
Delgado, J. (Updated 2009 August). Renal Function Markers - Kidney Disease. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/RenalFunctionMarkers.html?client_ID=LTD# through http://www.arupconsult.com. Accessed October 2009.
(© 2007). Estimated Glomerular Filtration Rate (eGFR), in the Detection and Assessment of Chronic Kidney Disease in Adults. LabCorp Technical Review [On-line information]. PDF available for download at https://www.labcorp.com/pdf/Estimated_Glomerular_Filtration_Rate_eGFRL1137_1207_2.pdf through https://www.labcorp.com. Accessed October 2009.
(Reviewed 2007 October). Glomerular Filtration Rate, Estimated (eGFR). Quest Diagnostics Test Summary [On-line information]. Available online at http://www.questdiagnostics.com/hcp/intguide/jsp/showintguidepage.jsp?fn=TS_eGFR.htm through http://www.questdiagnostics.com. Accessed October 2009.
Sources Used in Previous Reviews
National Kidney Foundation. DOQI: Clinical Practice Guidelines. Available online at http://www.kidney.org/professionals/kdoqi/guidelines through http://www.kidney.org.
National Kidney Foundation. Glomerular Filtration Rate. Available online at http://www.kidney.org/kidneydisease/ckd/knowGFR.cfm through http://www.kidney.org.
National Kidney Foundation. Kidney Learning System: GFR. Available online at http://www.kidney.org/professionals/KLS/gfr.cfm through http://www.kidney.org.
Levey et al. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group. Annals of Internal Medicine. 1999; 130(6):461-470.