What is Cys-C?

Cys-C(Cystatin C) is a low-molecular-weight (13 kDa), basic, non-glycosylated protein consisting of 122 amino acid residues and an isoelectric point of 9.3. Cys-C is a housekeeping gene that is expressed in almost all nucleated cells, has no histological specificity, and is produced at a stable rate.

Cys-C is not affected by inflammatory response, bilirubin, hemolysis, and triacylglycerol, and is independent of sex, age, and muscle mass. Because of its low relative molecular mass and high isoelectric point, Cys-C can freely pass through the glomerulus and then is reabsorbed and catabolized by epithelial cells in the proximal tubule, but not reabsorbed or secreted by the kidney tubules, making the kidney the sole site for clearance of Cys-C from the circulation.

Cys-C has specific physiological and biological properties and functions, so that it is more sensitive and specific in reflecting kidney diseases compared with other test indicators.

Clinical application of Cys-C

Under normal conditions, the concentration of Cys-C in serum and plasma is 0.51-1.09 mg/L (reference range). When kidney function is impaired, the concentration of Cys-C in blood varies with glomerular filtration rate. In kidney failure, the glomerular filtration rate decreases, and the concentration of Cys-C in the blood can increase by more than 10 times; if the glomerular filtration rate is normal and the tubular function is malfunctioning, it will prevent Cys-C from being absorbed in the tubules and broken down rapidly, so that the concentration in the urine will increase by more than 100 times.

Specific clinical applications of Cys-C are shown below:

① Evaluation of early impairment of kidney filtration function in diabetic kidney disease:Clinical testing of SCr to assess GFR lacks sufficient sensitivity for mild kidney injury, whereas Cys-C can respond sensitively to mild kidney injury, and regular testing of Cys-C in diabetic patients can be used to dynamically observe the progression of the disease.

② Evaluation of early impairment of kidney filtration function in hypertensive nephropathy.

③ Cys-C is a better indicator for differential diagnosis of mildly impaired renal function from normal function in patients with cirrhosis.

④ Cys-C has better value than blood Cr in assessing early kidney injury in patients with AKI and may provide a better chance for timely clinical treatment.

⑤ Cys-C has unique advantages for monitoring kidney function in children and is a more ideal marker for GFR in children over one year of age.

⑥ Cys-C is more sensitive than creatinine and creatinine clearance for detecting GFR after kidney transplantation and allows rapid diagnosis of acute rejection or kidney injury due to drug therapy.

⑦ Elevated Cys-C has an early warning effect on the development of diabetic kidney disease, predicts disease progression in diabetic nephropathy, and has some diagnostic and prognostic value.

⑧ Cys-C is predictive of chronic kidney failure in chronic heart failure and of worsening kidney function in acute heart failure.

Factors affecting Cys-C

Increased Cys-C levels may be due to:

Impaired kidney function

Thicker blood concentration

Decreased glomerular filtration rate

Chronic smoking, alcohol abuse, or frequent late nights

Hypertension, diabetic kidney disease, acute glomerulonephritis

Summary

The measurement of CysC has certain advantages in reflecting kidney diseases, and its blood concentration is determined by glomerular filtration rate without relying on the influence of any external factors, such as gender, age, and diet, which makes it an ideal endogenous marker reflecting the changes in glomerular filtration rate; it is also an important reference value and shows good application prospects in many fields, such as cardiac diseases, cerebrovascular diseases, and tumours.

The ReLIA Cys-C Immunoassay is CE-marked cleared. For more details on ReLIA Cys-C Immunoassay products and prices please contact us at  marketing@ReLIAchina.com

References

[1] LA Inker, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. New England Journal and Medicine. 2012; 367(1):20-29.

[2] A Haasefielitz, et al. Novel and conventional serum biomarkers predicting acute kidny injury in adult cadiac surgery—a prospective cohot study. Critical care Medicine. 2009;37(2):553-560.

[3] EL Knight, et al. Factors influencing serum cystatin C levels other than renal function and the impact on renal function measurement. Kidney International. 2004;65(4):1416-21.

[4] Shlipak MG, et al. Cystatin C and the risk of death and cardiovascular events among elderly persons. New England Journal and Medicine. 2005;352(20):2049-60.

[5] S Herget-Rosenthal, et al. Early detection of acute renal failure by serum cystatin C. Kidney Int. 2004; 66(3):1115-22.