The Cystatin C with eGFR test contains 1 test with 2 biomarkers.
Description: The Cystatin C with estimated Glomerular Filtration Rate (eGFR) test is a blood test used to assess kidney function. It measures the level of cystatin C, a small protein produced by all nucleated cells in the body, including the kidneys. The eGFR is calculated using the cystatin C level, along with other factors like age, gender, and race, to estimate the rate at which the kidneys are filtering waste products from the blood. This test is considered to be a more sensitive marker of kidney function compared to the traditional creatinine-based eGFR, especially in individuals with certain health conditions or those who may have muscle mass variations.
Also Known As: CysX Test, CysC Test, Cystatin C Test
Collection Method: Blood Draw
Specimen Type: Serum
Test Preparation: No preparation required
Average Processing Time: 4 to 5 days
When is a Cystatin C test ordered?
A Cystatin C with eGFR test may be ordered when a health care provider wants to assess kidney function in individuals at risk of kidney disease or those with known kidney dysfunction. Some common situations where the test may be ordered include:
Chronic Kidney Disease (CKD) Monitoring: Individuals with known CKD or those at risk of developing kidney disease may undergo this test regularly to monitor kidney function and evaluate disease progression.
Elderly Population: As kidney function naturally declines with age, the Cystatin C with eGFR test may be used in older adults to assess renal function more accurately.
Diabetes Management: People with diabetes are at a higher risk of kidney damage. This test may be used in conjunction with other kidney function tests to assess diabetic nephropathy.
Drug Toxicity Assessment: Certain medications can affect kidney function. The test may be used to monitor kidney function in patients taking medications that are potentially nephrotoxic.
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 Clearance
- Urine Albumin
- Lipid Panel
- Lipoprotein Fractionation Ion Mobility
- Blood Urea Nitrogen
- Comprehensive Metabolic Panel (CMP)
Conditions where a Cystatin C test is recommended:
The Cystatin C with eGFR test is particularly useful in assessing kidney function in various conditions, including:
Chronic Kidney Disease (CKD): To monitor and stage CKD, which is characterized by a gradual loss of kidney function over time.
Diabetes: To assess for kidney damage (diabetic nephropathy) in individuals with diabetes.
Elderly Population: To evaluate kidney function in the aging population, where kidney function may decline with age.
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.
Most Common Questions About the Cystatin C with eGFR test:
Understanding the Cystatin C with eGFR Test
What is the Cystatin C with eGFR test?
The Cystatin C with eGFR test is a blood test that helps evaluate kidney function. Cystatin C is a small protein produced throughout the body. The levels of this protein in blood can be used to calculate estimated Glomerular Filtration Rate (eGFR), which provides a measure of kidney function.
What is the purpose of the Cystatin C with eGFR test?
The purpose of the Cystatin C with eGFR test is to assess how well your kidneys are filtering small molecules like cystatin C from your blood. This test is often used when other tests of kidney function and structure might be unreliable.
When is the Cystatin C with eGFR test ordered?
The Cystatin C with eGFR test is ordered when a healthcare provider wants to evaluate a person's kidney function, particularly when other measures of kidney function might be affected by certain factors like age, sex, or muscle mass. It may also be ordered when there is a suspected kidney disease or when monitoring the kidney function of those with known kidney disease.
How often should the Cystatin C with eGFR test be done?
The frequency of testing depends on the individual's health status and whether they have a known condition that can affect kidney function. Your healthcare provider will determine the appropriate frequency of testing.
Interpreting Cystatin C with eGFR Test Results
What does a high Cystatin C level indicate in the Cystatin C with eGFR test?
An elevated level of cystatin C in the blood generally indicates decreased kidney function. The higher the cystatin C level, the lower the eGFR and the poorer the kidney function.
What does a low Cystatin C level indicate in the Cystatin C with eGFR test?
A low cystatin C level is generally associated with normal or high kidney function. However, cystatin C is typically used as a marker of impaired kidney function, so low levels are less commonly discussed.
Can the Cystatin C with eGFR test give false positive results?
Yes, certain factors such as thyroid dysfunction, inflammation, and certain medications can influence cystatin C levels, potentially leading to results that don't accurately reflect kidney function.
Can the Cystatin C with eGFR test give false negative results?
Yes, while less common, factors like low muscle mass and some medications can lower cystatin C levels, potentially masking kidney dysfunction.
Cystatin C with eGFR Test and Specific Conditions
Can the Cystatin C with eGFR test be used to diagnose kidney disease?
While cystatin C with eGFR is a useful test in evaluating kidney function, it isn't used alone to diagnose kidney disease. Other factors, such as other lab tests, symptoms, and medical history, also play a crucial role in diagnosis.
How does the Cystatin C with eGFR test relate to diabetes management?
Diabetes can lead to kidney damage over time. The cystatin C with eGFR test can help monitor kidney function in individuals with diabetes, potentially catching kidney damage early.
How does the Cystatin C with eGFR test relate to hypertension management?
Hypertension, or high blood pressure, can also damage the kidneys. The cystatin C with eGFR test can help monitor kidney function in individuals with hypertension, allowing for early detection of potential kidney damage.
Can the Cystatin C with eGFR test diagnose acute kidney injury?
Elevated cystatin C levels can indicate acute kidney injury, but the diagnosis also involves other factors like clinical signs and symptoms and other lab tests.
Can the Cystatin C with eGFR test predict the risk of cardiovascular disease?
Research suggests that elevated cystatin C levels, even in the absence of kidney disease, may be associated with an increased risk of cardiovascular disease. However, more research is needed in this area.
How does the Cystatin C with eGFR test relate to the management of chronic kidney disease (CKD)?
In people with CKD, the cystatin C with eGFR test is a valuable tool for monitoring kidney function over time and adjusting treatment as necessary.
General Questions About the Cystatin C with eGFR Test
Can the Cystatin C with eGFR test be used to monitor the effects of kidney disease treatment?
Yes, changes in cystatin C levels and eGFR over time can help a healthcare provider determine whether a treatment is working.
Can I have a normal Cystatin C with eGFR test result and still have kidney disease?
Yes, early in kidney disease, your cystatin C level and eGFR might still be normal. As kidney function declines, these values will change.
Can the Cystatin C with eGFR test be used in children?
Yes, the cystatin C with eGFR test can be used in children. It's especially useful in children because, unlike creatinine-based eGFR calculations, it's not affected by muscle mass.
What other tests might be done with the Cystatin C with eGFR test?
Other tests that may be done with the Cystatin C with eGFR test include blood urea nitrogen (BUN), creatinine, urinalysis, and urinary albumin to creatinine ratio (ACR).
Is the Cystatin C with eGFR test used in people undergoing chemotherapy?
Yes, some chemotherapy drugs can affect kidney function. The cystatin C with eGFR test may be used to monitor kidney function in these individuals.
How does the Cystatin C with eGFR test differ from a creatinine-based eGFR test?
Cystatin C levels are less affected by factors such as age, sex, and muscle mass, making it a more reliable indicator of kidney function in some cases compared to creatinine-based eGFR.
Can the Cystatin C with eGFR test detect early kidney damage due to medication toxicity?
Yes, since cystatin C levels rise with decreased kidney function, the test may be able to detect early kidney damage due to certain medications.
Does inflammation or infection affect the Cystatin C with eGFR test?
Yes, some studies suggest that inflammation and infection can increase cystatin C levels independent of kidney function. This is why it's important to interpret the test results in the context of the individual's overall health situation.
Can the Cystatin C with eGFR test be used in the elderly?
Yes, the test can be used in the elderly. It may be particularly useful in this population as muscle mass, which affects creatinine-based eGFR, often declines with age.
How does the Cystatin C with eGFR test compare to a kidney biopsy for diagnosing kidney disease?
While a kidney biopsy can provide detailed information about the structure and health of the kidneys, it's an invasive procedure. The cystatin C with eGFR test is a less invasive test that provides information about kidney function, not structure.
Are there any conditions that may affect the Cystatin C with eGFR test results?
Yes, conditions such as hyperthyroidism and inflammation, and use of corticosteroids, can affect cystatin C levels. It's important for your healthcare provider to be aware of your overall health situation when interpreting the results.
We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.