Cystatin - C Test

The cystatin C test is a blood test that measures the level of cystatin C, a small protein produced by nearly all cells in the body. The cystatin C and GFR (glomerular filtration rate) are closely related because cystatin C levels are used to estimate the GFR, which reflects how well the kidneys filter waste from the blood. When the kidneys do not function well, cystatin C levels in the blood increase because the kidneys cannot remove it properly.

The cystatin C test is used to detect early kidney disease and monitor the progression of chronic kidney disease (CKD). It is often used together with the serum creatinine test. However, creatinine levels can be affected by muscle mass, age, and other factors; in these cases, the cystatin C test might give a more accurate result.

The cystatin C test price may vary by laboratory, city, and whether any additional tests are included in the package.

The cystatin C test may be recommended when a doctor needs a clearer picture of kidney function, particularly when creatinine test results may be affected by factors such as age and muscle mass.

Your doctor may recommend this test if:

• You have signs or symptoms of kidney disease, such as swelling of the hands, feet, or face, changes in urination, fatigue, or high blood pressure.
• You have CKD and need regular monitoring of kidney function.
• Your doctor needs a more precise estimate of your GFR.

Categories of people who should consider the Cystatin C Test

• People with diabetes, high blood pressure, or a family history of kidney disease – These conditions increase the risk of kidney disease.
• People with symptoms that indicate kidney disease – Symptoms include fatigue, swollen ankles, feet, and hands, changes in urine output, unexplained nausea, vomiting, and weight loss.
• Older adults or people with very low or very high muscle mass – The test provides a more reliable assessment of kidney function in these individuals, especially when the creatinine test results are unreliable.
• People who have had a kidney transplant – The test helps monitor kidney function.

The cystatin C test is not a routine screening test. It is performed when your doctor needs a more accurate assessment of kidney function or to monitor kidney disease over time.

The test may help detect or monitor the following conditions:

• CKD: Cystatin C can help detect early changes in kidney function and identify CKD before symptoms develop.
• Reduced GFR: Cystatin C is used to estimate GFR, which indicates how efficiently the kidneys are removing waste products from the blood.
• Cardiovascular disease risk: Higher cystatin C levels have been associated with an increased risk of heart problems, particularly in people with CKD. However, the test is not used alone to diagnose heart disease.

What to Expect Before the Cystatin-C Test

No fasting is required for a standalone cystatin-C test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise cystatin-C levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the Cystatin-C Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

The test includes the following parameter:

• The concentration of cystatin C in the blood.

The normal range of cystatin C varies with age and may differ slightly between laboratories depending on the testing method used. The reference ranges in this report are:

The cystatin C test measures the cystatin C level in the blood to assess kidney function. The results are interpreted together with your medical history, symptoms, serum creatinine, estimated GFR (eGFR), and other laboratory findings.

The cystatin C test is a simple blood test and carries very little risk.

Potential Risks and Complications

• Slight pain or discomfort at the site where the needle is inserted.
• Mild bruising at the puncture site.

Understanding the Cystatin C Test Limitations

• The cystatin C test cannot determine the exact cause of reduced kidney function. Additional tests may be needed to identify the underlying condition.
• The test results may be less accurate in people with untreated thyroid disorders or those taking corticosteroid (steroid) medications.
• The test results should be interpreted together with your medical history, physical examination, and other kidney function tests.

Depending on the results of the cystatin C test, your doctor may recommend additional tests to assess kidney function and determine the underlying cause of abnormal results.

• Serum creatinine test
• eGFR test
• Urine albumin test