Cystatin C with eGFR Most Popular

The Cystatin C with eGFR test contains 1 test with 2 biomarkers.

Description: The Cystatin C blood test is used to determine kidney health by measuring levels of the protein Cystatin C.

Also Known As: CysX Test, CysC Test, Cystatin C Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is a Cystatin C test ordered?

Studies are confirming and defining the utility of cystatin C, particularly as an early, sensitive diagnostic for chronic kidney disease. It may be requested if a person has a known or suspected condition that affects or may influence kidney function and reduces the glomerular filtration rate, which is the rate at which the kidneys filter pollutants from the blood.

It may be ordered if a healthcare provider is dissatisfied with the results of previous tests, such as a creatinine or creatinine clearance, or wants to check for early renal dysfunction, especially in the elderly or unwell babies, and/or wants to track known impairment over time.

The study of cystatin C as a predictor of end-stage renal disease, heart failure, and death is still underway. Cystatin C, when paired with blood creatinine in an equation, has been found to increase the estimation of GFR in a variety of populations.

What does a Cystatin C blood test check for?

Cystatin C is a tiny protein generated by all cells with a nucleus and found in a number of body fluids, including the blood. It is constantly created, filtered from the blood by the kidneys, and broken down. This test evaluates kidney function by measuring the level of cystatin C in the blood.

The glomeruli, clusters of microscopic blood capillaries in the kidneys that allow water, dissolved substances, and wastes to flow past their walls while holding blood cells and bigger proteins, filter cystatin C out of the blood. Filtrate fluid is made up of what goes through the glomeruli's walls. The kidneys reabsorb cystatin C, glucose, and other chemicals from this fluid. The remainder of the fluid and wastes are transported to the bladder and expelled as urine. The cystatin C that has been reabsorbed is then broken down and not reintroduced to the bloodstream.

The glomerular filtration rate is the rate at which the fluid is filtered. The GFR falls as kidney function declines, whereas cystatin C and other renal function indicators such as creatinine and urea in the blood rise. These levels rise because the kidneys are unable to filter the blood correctly at a regular rate, resulting in their buildup in the blood. Improvements in kidney function, on the other hand, are predicted to lead to increases in GFR, which will result in lower levels of cystatin C, creatinine, and urea as the kidneys are better able to remove them from the blood.

Cystatin C concentrations in the blood are stable while the kidneys are working properly. The concentrations begin to grow as renal function deteriorates. This rise in cystatin C occurs when GFR declines and is generally apparent before kidney function declines significantly.

The cystatin C test has gained popularity as a technique of measuring kidney function since cystatin C levels fluctuate with changes in GFR. Creatinine, a result of muscle metabolism that is detected in the blood and urine, blood urea nitrogen, and eGFR are currently employed tests. Cystatin C, unlike creatinine, is unaffected by muscle mass, race, or diet, leading to the hypothesis that it could be a more trustworthy measure of renal function and so used to provide a more precise estimate of GFR.

While there is increasing evidence and literature to support the use of cystatin C, there is still some debate over when and how it should be administered. However, testing is becoming more widely available, and measures are being conducted to standardize cystatin C results calibration.

Lab tests often ordered with a Cystatin C test:

  • Creatinine
  • Creatinine Clearance
  • Urine Albumin
  • Lipid Panel
  • Lipoprotein Fractionation Ion Mobility
  • Blood Urea Nitrogen
  • Comprehensive Metabolic Panel (CMP)

Conditions where a Cystatin C test is recommended:

  • Kidney Disease
  • Diabetes

How does my health care provider use a Cystatin C test?

In those who have known or suspected renal disease, a cystatin C test can be used instead of creatinine and creatinine clearance to screen for and monitor kidney dysfunction. It's especially beneficial in circumstances where creatinine measurements aren't accurate.

Creatinine measurements may not be trustworthy in people who have liver cirrhosis, are very fat, are malnourished, follow a vegetarian diet, have amputated limbs, or have reduced muscle mass. Because creatinine is dependent on muscle mass, assessing kidney function in people with abnormally high or low body mass may be inaccurate. Cystatin C is a more reliable indicator of renal function than creatinine since it is unaffected by body mass or diet.

When other test findings are normal or borderline, and an affected person has few, if any, symptoms, measuring cystatin C may be helpful in early diagnosis of kidney disease. In this scenario, the healthcare provider may wish to measure cystatin c to see if chronic renal disease is present.

Other applications of cystatin C are being investigated, such as measuring glomerular filtration rate using it alone or in combination with blood creatinine. An equation for eGFR that incorporates both creatinine and cystatin C was found to be more accurate than one that utilizes either of these alone in a recent study, and could be used to diagnose chronic kidney disease in persons with an eGFR near 60, the CKD threshold. It has been linked to a higher risk of mortality, cardiovascular disease, and heart failure in older persons, in addition to kidney impairment. Before being completely integrated into clinical practice, these equations are now being validated in various patient populations.

Finally, some study suggests that cystatin C returns to normal faster than creatinine, and that it could be used to assess renal function and severity of sickness in critically ill hospitalized patients when GFR is rapidly changing.

What do my Cystatin C test results mean?

A high amount of cystatin C in the blood indicates a lower glomerular filtration rate and, as a result, kidney failure.

Because cystatin C is made at a constant rate throughout the body and eliminated and broken down by the kidneys, it should stay at a constant level in the blood if the kidneys are healthy and the GFR is normal.

Increased levels of cystatin C have been linked to an increased risk of heart disease, heart failure, and mortality in recent investigations.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.



*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

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