9393. Cystatin C

Cystatin C is a protein involved in the physiological processes of virtually all cells in the body. It is eliminated from the body by the kidneys, and its levels are directly dependent on proper kidney function. As a result, it is one of the most accurate indicators of pathological changes in the kidneys.

The test is used to diagnose impaired glomerular filtration in the kidneys. It should be evaluated in conjunction with creatinine, urea, blood urea nitrogen, potassium, calcium, magnesium, and sodium.

Cystatin C is synthesized by all cells and is present in all biological fluids. Under normal conditions, it is freely filtered by the glomeruli and reabsorbed in the renal tubules. As a result, cystatin C levels remain relatively stable in the systemic circulation. These properties make cystatin C a marker that reflects the glomerular filtration rate (GFR).

Decreased kidney function leads to a reduction in GFR (the rate at which blood is filtered) and an increase in the levels of cystatin C and other markers of kidney function, such as creatinine and urea in the blood. Cystatin C is a sensitive marker of impaired kidney function, particularly in the absence of elevated creatinine concentrations.

Creatinine is a reliable indicator of kidney function and, unlike cystatin C, is influenced by factors such as age, sex, muscle mass, dietary habits, physical activity, and race. Thus, kidney function may decline by more than 50% before the creatinine level exceeds the upper limit of the reference range.

• For the diagnosis and monitoring of impaired renal excretory function.
• For the early diagnosis of diabetic nephropathy.
• For selecting the dosage of potentially nephrotoxic medications and for assessing the nephrotoxicity of radiographic contrast agents.

• Venous blood

In order to exclude factors that may affect the test results, we recommend to follow the preparation rules: