Cystatin C Test

The cystatin C test is a blood test to determine the working status of the kidneys. Cystatin C is a protein synthesised continuously by the body cells and it is found in the body fluids including blood, spinal fluid and breast milk. Healthy kidneys filter the cystatin C from the blood which is then excreted out in the urine. This keeps the level of cystatin C in the blood at an optimum level. When there is a kidney malfunction, the level of cystatin C in the blood becomes too high. This test helps your doctor to find the GFR (glomerular filtration rate) of your kidneys.

It is recommended that you wear a sleeveless or short-sleeved shirt or a full-sleeved shirt with sleeves rolled up to enable easy withdrawal of blood from your arm. No test preparation is required. There are no dietary restrictions that you have to follow before the test. Certain medications that you are currently taking may affect the test results. So, make sure to inform your doctor regarding all the medications, vitamins, herbs and supplements you are taking. In case the blood withdrawn is to be used for further tests, your doctor will inform you the necessary preparations in prior.

Cystatin C varies less with factors like age, race and muscle mass. Hence it serves as a reliable indicator of kidney function. Measuring cystatin C levels can be useful for early detection of kidney diseases as other indicators like eGFR, creatinine or urine albumin may still be normal.

A few millilitres of blood sample is required for this test. This will be obtained directly from your arm. The insertion site is prepared for the withdrawal of blood. An elastic band is wrapped around your arm to make the veins swell with blood. The site to be injected is cleansed with antiseptic. The needle is inserted into the vein and a tube attached to the needle is then filled up with blood. A gauze pad or cotton ball is placed over the punctured area as the needle is removed. The sample is transferred to the laboratory for further examination.