Cystatin C With Glomerular Filtration Rate, Estimated (eGFR)
Also known as: Cystatin C, eGFR, Estimated Glomerular Filtration Rate, GFR, Estimated
Use
Since it is formed at a constant rate and freely filtered by the healthy kidney, cystatin C is a good marker of renal function. Serum concentrations of cystatin C are almost totally dependent on glomerular filtration rate (GFR). A reduction in GFR causes a rise in the concentration of cystatin C.1,2
Special Instructions
Overnight fasting is preferred for patient preparation. If a green-top (heparin) tube is used, plasma should be separated from red blood cells and transferred to a transfer tube.
Limitations
Cystatin C values are not affected by muscle mass or nutrition, unlike creatinine. However, creatinine levels do not indicate a rise until the GFR has decreased by about 50%, highlighting the importance of cystatin C in early CKD detection. Its utility is thus limited in circumstances where only creatinine-based assessments are needed or when unrelated renal pathologies influence the GFR.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 87430-5
- 33863-2
- 50210-4
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Gel-barrier tube or green-top (heparin) tube
Collection Instructions
If green-top (heparin) tube is used, separate plasma from red blood cells and transfer plasma to a transfer tube.
Patient Preparation
Overnight fasting is preferred.
Storage Instructions
Usually stored at room temperature.
Causes for Rejection
Specimen other than serum or heparinized plasma, grossly hemolyzed (>1,000 mg/dL Hgb) samples, excessive turbidity and clots in samples
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days at 15°C to 25°C |
| Refrigerated | 7 days at 2°C to 8°C |
| Frozen | 6 months at -20°C |