Cystatin C

Maintaining healthy kidney function is crucial for overall well-being. The Cystatin C test offers essential insights into kidney filtration. IntroLab in Belgrade specializes in providing this test.

What is Cystatin C?

Cystatin C is a low molecular weight biomarker (13.4 kDa) used to assess kidney function. This protein is produced by all nucleated cells at a constant rate. It is eliminated from the plasma through glomerular filtration and is then completely metabolized in the proximal tubules of the kidneys. A key characteristic of Cystatin C is that it is not normally excreted in the urine, meaning it is absent in the urine of healthy individuals.

Why is the Cystatin C test performed?

This test is essential for evaluating the glomerular filtration rate (GFR), a key measure of kidney function. When kidneys are healthy, Cystatin C levels in the blood remain stable. However, if kidney function declines and GFR decreases, Cystatin C levels in the blood rise, indicating potential kidney dysfunction or damage.

When is the test performed?

The Cystatin C test is usually recommended in the following situations:

• When there is suspicion of kidney disease, such as chronic kidney disease, kidney damage, or kidney inflammation.
• When standard creatinine tests are unreliable, which can occur in medical conditions like liver cirrhosis, malnutrition, or in individuals who engage in bodybuilding.
• In patients whose tests for eGFR (estimated glomerular filtration rate), creatinine, or urine albumin are normal or borderline, but kidney damage is still suspected.

Interpreting results

Interpreting the results of the Cystatin C test involves evaluating the level of this protein in the blood and its relation to kidney function. Key points for interpretation include:

• Normal Values: Typical Cystatin C levels usually range between 0.5-1.0 mg/L, but can vary depending on the laboratory, as well as the patient’s gender and age.
• Increased Values: Elevated concentrations can indicate a reduced glomerular filtration rate (GFR) and kidney dysfunction. This may be due to conditions such as chronic kidney disease, acute kidney injury, diabetes, hypertension, or other factors affecting kidney function.
• Decreased Values: Lower Cystatin C levels are not diagnostically significant and usually do not indicate kidney problems. In some cases, lower levels may be associated with factors such as increased muscle mass or pregnancy.
• Combination with Other Markers: The Cystatin C test is sometimes combined with other kidney function markers, such as creatinine, to provide a more comprehensive assessment of kidney health.

Advantages of the Cystatin C test over other markers

The Cystatin C test offers several advantages over other kidney function markers. Unlike creatinine, the level of Cystatin C in the blood is not affected by gender, muscle mass, age, race, or dietary habits. This consistency makes Cystatin C a more reliable indicator of kidney function.

Compared to creatinine and eGFR (estimated glomerular filtration rate), Cystatin C provides a more accurate assessment of kidney health. Creatinine and eGFR can be unreliable in certain conditions, such as liver cirrhosis, malnutrition, or in individuals who engage in bodybuilding. In these cases, the Cystatin C test can deliver more precise information about kidney function, enabling better management and monitoring of kidney diseases.

Importance of consistency and context in interpreting Cystatin C test results

It is important to note that Cystatin C test results can vary between different laboratories due to differences in testing methods and manufacturer specifics. Therefore, it is recommended to monitor Cystatin C levels at the same laboratory to ensure consistent results.

Additionally, Cystatin C test results do not definitively indicate the presence or absence of disease. They are only one part of a broader diagnostic picture and should be interpreted alongside other tests and the patient’s clinical condition. This comprehensive approach enables healthcare professionals to make the most accurate diagnosis and determine the most effective treatment plan.