N Latex Cystatin C Assay
Assay for Early Detection of Decline in Renal Function
Cystatin C is a nonglycated, low-molecular-weight (13 kDa) protein that is synthesized by all nucleated cells. It is produced at a constant rate regulated by a housekeeping gene.1 Cystatin C is freely filtered by the glomerulus, and there is no tubular secretion or any extrarenal elimination. In addition, cystatin C is not affected by muscle mass, diet, gender, or inflammation.
The relevance of determining cystatin C for diagnosis in CKD is included in the international KDIGO (Kidney Disease Improving Global Outcomes) guidelines.2
No tubular secretion; sensitive in the creatinine-blind range1
- Higher sensitivity in early disease
Independent of age, sex, and muscle mass1
- Constant relationship between cystatin C and glomerular filtration rate (GFR) at 1 year of age and older
- Single reference range: 0.62–1.11 mg/L in children and adults ranging in age from 1 to 78 years
- Sensitive detection of declining GFR with aging
- Reliable in patients with spina bifida, paralysis, amputations, etc.
High correlation to GFR reference methods1; high correlation to GFR decline
- High reliability and accuracy
Increased sensitivity compared to creatinine in liver disease patients3 or by creatinine intake. Cystatin C levels may be influenced by high-dose steroid therapy or thyroid dysfunction.
No analytical interferences known
1. Newman DJ. Cystatin C. Ann Clin Biochem. 2002;39:89-104.
2. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Official Journal of the International Society of Nephrology. 2013;3:1-5.
3. Woitas RP, Stoffel-Wagner B, Flommersfeld S, et al. Correlation of serum concentrations of cystatin C and creatinine to inulin clearance in liver cirrhosis. Clin Chem. 2000;46:712–15