Cystatin C may be used as an alternative to creatinine and creatinine clearance to screen for and monitor kidney dysfunction in those with known or suspected kidney disease. It may be especially useful in those cases where creatinine measurement is not appropriate, for instance, in those who have liver cirrhosis, are very obese, are malnourished, or have reduced muscle mass. Measuring cystatin C may also be useful in the early detection of kidney disease when other test results may still be normal and an affected person may have few, if any, symptoms.
Researchers are exploring other uses of cystatin C, such as using it alone or in combination with blood creatinine for estimating the glomerular filtration rate (GFR). A recent study found that an equation for eGFR that includes both creatinine and cystatin C was more accurate than one that uses either of these alone and could be used to confirm chronic kidney disease (CKD) in people with an eGFR near 60, the threshold for CKD. In addition to kidney dysfunction, it has been associated with an increased risk of cardiovascular disease and heart failure in older adults.
Cystatin C is gaining acceptance as studies confirm and define its usefulness, especially as an early, sensitive marker for chronic kidney disease (CKD). It may be ordered when a person has a known or suspected disease that affects or potentially affects kidney function and reduces the rate at which the kidneys filter impurities from the blood, the glomerular filtration rate (GFR). It may be ordered when a health practitioner is not satisfied with the results of other tests, such as a creatinine or creatinine clearance, or wants to check for early kidney dysfunction, particularly in the elderly, and/or wants to monitor known impairment over time.
Research is ongoing to learn more about cystatin C as an indicator of risk of end stage renal disease, heart failure, and death. Studies have also found that, in diverse populations, cystatin C may improve the estimate of GFR when combined in an equation with blood creatinine.
An high level of cystatin C in the blood corresponds to a decreased glomerular filtration rate (GFR) and hence to kidney dysfunction. Since cystatin C is produced throughout the body at a constant rate and removed and broken down by the kidneys, it should remain at a steady level in the blood if the kidneys are working efficiently and the GFR is normal.
Corticosteroids can increase levels cystatin C levels while cyclosporine can decrease them.
Cystatin C has been associated with hyperhomocysteinemia (increased homocysteine), which is often found in kidney transplant patients, and it has been shown to increase with the progression of liver disease. At least one study has looked at comparing cystatin C levels in serum with that found in pleuraleffusion to help determine the cause of the effusion. These associations may or may not prove clinically useful.
In the absence of kidney disease, cystatin C levels may be elevated in rheumatic diseases and in malignant diseases, although they are not affected by tumor burden, the amount of cancer that someone has.
This article was last reviewed on October 25, 2013. | This article was last modified on April 3, 2014.
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