Specimen Collection Manual and Test Catalog

2 mL serum or plasma; minimum 0.5 mL

Allow serum to clot. Centrifuge to separate serum or plasma within 2 hours of collection.

Refrigerated (2-8°C) preferred or frozen

Room temperature or refrigerated: stable 7 days. Frozen serum stable 24 months for Cystatin C; 3 months for creatinine. Frozen plasma 6 months for Cystatin C, 3 months for creatinine.

Stability limits exceeded

Cystatin C: 
18-49 years: 0.63-1.03 mg/L 
> or =50 years: 0.67-1.21 mg/L 
<18 years: Undefined 

Creatinine: 
Less than 2 years: 0.1-0.4 mg/dL 
2 years to <6 years: 0.2-0.5 mg/dL 
6 years to <10 years: 0.3-0.6 mg/dL 
10 years to <18 years: 0.4-1.0 mg/dL 
Females 18 years or older: 0.5-1.0 mg/dL 
Males 18 years or older: 0.6-1.2 mg/dL

Estimated Glomerular Filtration Rate (eGFR) is calculated based on 2012 CKD-EPI Cystatin C equation and 2021 CKD-EPI equations. EGFR Calculator | National Kidney Foundation. eGFR >=60 mL/min is considered normal in most case.

Cystatin C with Estimated GFR, Creatinine

CysC, CREATB, Creatinine-S

Serum Cystatin C with Creatinine is useful in the evaluation of kidney function. An estimated glomerular filtration rate (eGFR) will accompany all serum or plasma Cystatin C, Creatinine results.