Cystatin C with Glomerular Filtration Rate, Estimated (eGFR)
Test Summary
Cystatin C is a non-glycosylated, low molecular weight (13,250 kD) cysteine proteinase inhibitor that is produced by all nucleated cells and found in body fluids, including serum. Since it is formed at a constant rate and freely filtered by the kidneys, its serum concentration is inversely correlated with the glomerular filtration rate (GFR); that is,high values indicate low GFRs while lower values indicate higher GFRs, similar to creatinine. The renal handling of cystatin C differs from creatinine. While both are freely filtered by glomeruli, once it is filtered, cystatin C, unlike creatinine, is reabsorbed and metabolized by the proximal renal tubules. Thus, under normal conditions, cystatin C does not enter the final excreted urine to any significant degree. The serum concentration of cystatin C remains unchanged with infections, inflammatory or neoplastic states, and is not affected by body mass, diet, or drugs. Thus, cystatin C may be a more reliable marker of renal function (GFR) than creatinine. GFR can be estimated (eGFR) from serum cystatin C utilizing an equation which includes the age and gender of the patient. The CKD-EPI cystatin C equation was developed by Inker et al, and demonstrated good correlation with measured iothalamate clearance in patients with all common causes of kidney disease, including kidney transplant recipients. Cystatin C eGFR may have advantages over creatinine eGFR in certain patient groups in whom muscle mass is abnormally high or low (for example quadriplegics, very elderly, or malnourished individuals). Blood levels of cystatin C also equilibrate more quickly than creatinine, and therefore, serum cystatin C may be more accurate than serum creatinine when kidney function is rapidly changing (for example amongst hospitalized individuals).
Aliases
- CysC
Specimen Collection
Special Instructions
N/A
Preferred Specimen
1 mL serum
Minimum Volume
0.5 mL
Instructions
Barrier tubes (serum separator tubes or plasma separator tubes) are preferred. If non-barrier tubes are utilized, the serum/plasma must be removed immediately after centrifuging and placed in a screw-cap transfer tube.
Collection notes: Avoid hemolysis. Invert tubes at least 8 times. Allow to clot in an upright position for 30 minutes. Within 2 hours, centrifuge tubes 10 minutes. Keep tightly stoppered.
Do NOT re-centrifuge tubes. Do NOT freeze the primary collection tube.
Patient Preparation
N/A
Storage
N/A
Transport Temperature
Room Temperature
Specimen Stability
- Room temperature: 7 days
- Refrigerated: 7 days
- Frozen: 24 months
Limitations
N/A
Other Acceptable Specimens
Plasma from Lithium Heparin (Light Green Top) tube
Unacceptable Specimens
Blood collected in capillary blood collection tubes is unsuitable for use with our assay
Order Code
EPIC (Premier) Code
LAB6943
Includes
- Cystatin C
- eGFR
CPT Code
- 82610
Billing Code
- 300124
CPT Statement
Methodology
Particle Enhanced Turbidimetric Immunoassay (PETIA)
FDA Status
FDA Approved
Physician Attestation of Informed Consent
N/A
Testing Laboratory
2308 Sandridge Drive
Moraine OH, 45439
Department
Reference Range
See Laboratory Report
Setup Schedule / Expected Turnaround Time
24/7; Report available: Daily
Specimen Collection
Special Instructions
N/A
Preferred Specimen
1 mL serum
Minimum Volume
0.5 mL
Instructions
Barrier tubes (serum separator tubes or plasma separator tubes) are preferred. If non-barrier tubes are utilized, the serum/plasma must be removed immediately after centrifuging and placed in a screw-cap transfer tube.
Collection notes: Avoid hemolysis. Invert tubes at least 8 times. Allow to clot in an upright position for 30 minutes. Within 2 hours, centrifuge tubes 10 minutes. Keep tightly stoppered.
Do NOT re-centrifuge tubes. Do NOT freeze the primary collection tube.
Patient Preparation
N/A
Storage
N/A
Transport Temperature
Room Temperature
Specimen Stability
- Room temperature: 7 days
- Refrigerated: 7 days
- Frozen: 24 months
Limitations
N/A
Other Acceptable Specimens
Plasma from Lithium Heparin (Light Green Top) tube
Unacceptable Specimens
Blood collected in capillary blood collection tubes is unsuitable for use with our assay
Result Information
Methodology
Particle Enhanced Turbidimetric Immunoassay (PETIA)
Testing Laboratory
Reference Range
See Laboratory Report
Setup Schedule / Expected Turnaround Time
24/7; Report available: Daily