Since the concentration of cystatin C in the blood will not change due to infection or inflammation and isn't affected by body weight, drugs or diet - cystatin C level could be a more reliable indicator of kidney health than creatinine (2).
Testing for cystatin may also be useful to detect kidney disease early when the affected person isn't experiencing many (if any) symptoms, and other test results are normal.
What is Cystatin C?
Cystatin C is a protein found in almost all the cells in the body. Cystatin C helps to regulate the activity of enzymes needed to break down bigger molecules both inside of and around those cells (3).
Cystatin C level in the blood can be measured to determine how well the kidneys are functioning (3). The kidneys, liver, and spleen all work to filter the blood and excrete any waste substances as urine. This filtration process happens in a microscopic structure in the kidneys; the glomerulus (4). Each kidney contains approximately one-million glomeruli that function as tiny sieves to extract waste. The glomerular filtration rate (GFR) rate is a measure of how well the glomeruli are filtering blood (4).
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