CPT Code:


Test Type: Serum Kit Based
Stability Time:


Refrigerated: 3 days

Reference Range:
  • Normal: ≤1.20 mg/L
  • High: >1.20 mg/L


Cystatin C is a protein produced by all nucleated cells at a constant rate. It is the most reliable available serum marker of kidney function and is superior to creatinine in estimating glomerular filtration (eGFR) rate as it is much less affected by age, gender, muscle mass, and/or ethnic background.

Methodology - Immunoturbidimetric Assay

Collection Details:

Collection Instructions:

Preferred Specimen

1.0 mL serum (0.5 mL minimum) collected in serum separator tube (Tiger Top)

Alternate Specimen

1.0 mL EDTA plasma (0.5 mL minimum) collected in plasma separator tube (Pearl Top)

Transport Temperature

Refrigerated (ship on frozen cold packs)