- Estimated Glomerular Filtration Rate
Creatinine is a waste product that is produced by normal muscle activity, and blood levels usually do not change day-to-day. Creatinine is excreted by the kidneys, and blood levels are used to diagnose kidney function. Creatinine clearance directly measures how quickly the kidney cells are able to filter waste products from your blood. Creatinine clearance levels normally decrease at a steady and predictable rate after the age of 40, due to normal damage to the kidney cells that filter waste products from the blood.
Since the 24 hour urine test is expensive and takes a long time to run, a mathematical calculation called the Estimated Glomerular Filtration Rate (EGFR) has been developed that is quicker and more accurate. This calculation uses creatinine blood levels, age, and set values (determined by race and gender) to estimate how long it should take the kidney cells to filter out waste products from your blood. EGFR is now used routinely as an indication of kidney health, with the result that more people are being diagnosed earlier with chronic renal failure, allowing for early treatment and the prevention of complications of kidney disease.
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