eGFR

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.

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.

No test preparation is needed.