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Cystatin C is a protein produced by all cells that contain a cell nucleus. It is an inhibitor of cysteine proteinase. Cystatin C is present in all body fluids in the body. It undergoes filtration in the renal glomeruli, resorption and degradation in the cells of the proximal tubules.
What is Cystatin C?
Cystatin C is a protein belonging to cysteine proteinases. It is produced by cells with a cell nucleus in their structure. This protein is found in the human body in all body fluids. It is considered to be one of the most important indicators of kidney disease, which has gained a reputation as a civilization disease. Cystatin C testing is much more sensitive than GFR or creatinine, and for this reason it is much more often chosen. Not so long ago, creatinine was considered the key research. It is the end product of muscle metabolism and is completely filtered in the kidneys. However, there are some limitations to the creatinine test:
- płec,
- age,
- muscle mass,
- diet,
- the intensity of physical activity.
Cystatin C determination is performed when there is a suspicion of renal dysfunction and in obese or malnourished people. In addition, it is used in monitoring patients taking nephrotoxic preparations and after kidney transplantation.
When do we perform a cystatin C test?
We perform cystatin C testing in the following cases:
- Suspicion of acute and chronic renal failure.
- Assessment of the excretory function of the kidneys.
- Controlling patients treated with nephrotoxic preparations.
- Diagnose Diabetic Nephropathy.
- Controlling GFR in kidney transplant patients.
- Assessing the risk of developing cardiovascular problems or heart failure (especially in the elderly).
- Monitoring of kidney function in people with chronic diseases in the course of which the kidneys may be damaged.
Cystatin C – study
Cystatin test material: serum.
Preparation for the test: on an empty stomach (at least 8 hours).
The course of the study: one-time blood sampling from a vein in the arm, which is then placed in a special test tube.
Waiting time for the cystatin result: 1 Day. The cost of the examination without a doctor’s referral is between PLN 50-100.
Norma cystatyny C: 0,47-1,03 mg/l.
Comments: Glomerular filtration impairment index. The concentration of cystatin increases as the glomerular filtration rate (GFR) decreases. Currently, it has no clinical application – this parameter is used to evaluate the excretory function of the kidneys in research.
You should know that elements such as:
- disorders in the collection of urine,
- intense physical effort on the day preceding the examination and on the day of the examination,
- too little hydration of the patient’s body,
may disturb the reliability of the creatinine result.
Cystatin norms in adults and children
The concentration of cystatin C in the blood depends on the speed of its glomerular filtration. Contrary to the creatinine test, the determination of cystatin is not influenced by the age and sex of the examined person, their diet or hormonal stress.
Reference values for cystatin C:
- children up to 1 year of age – 0,59-1,97 mg / l,
- children 1-18 years old – 0,50-1,27 mg / l,
- adults up to 50 years of age – 0-53 mg / l,
- adults over 50 – 0-58 mg / l.
Standards may vary from lab to lab.
Cystatin C – test interpretation
The concentration of cystatin C increases with progressive kidney damage. Increased values of Cystatin C above the norm 0,47-1,03 mg / l. may testify to:
- with impaired kidney function and reduced glomerular filtration,
- about liver problems,
- about rheumatic problems,
- about cancer,
- about the use of drugs, e.g. corticosteroids that increase the concentration of cystatin.
- have a higher risk of heart disease and stroke
- o hyperhomocysteinaemia in renal transplant patients.
In each case, the patient should refer the test result to a specialist who will assess the test results himself. It happens that it is necessary to repeat it or conduct additional tests.