| Laboratory: | Clinical Biochemistry (SENDOUTS) | ||||
| Test Name: |
CYSTATIN C - (S) or (P)
Test Code:
MIS8
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| Clinical Information: |
Description: Cystatin C (CysC) may have advantages over creatinine eGFR in certain patient groups in whom serum creatinine may not be a reliable marker of renal function.
Cystatin C is a low molecular weight (13,250 kD) cysteine proteinase inhibitor that is produced by all nucleated cells and found in body fluids, including serum. It is formed at a constant rate and freely filtered by the kidneys, and 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. Both creatinine and CysC are freely filtered by glomeruli; however CysC, is reabsorbed and metabolized by proximal renal tubules. Under normal conditions, significant CysC does not enter the urine. See below attached Cystatin C Testing Indications in Patients 11-Jan-24 for full indications. Cystatin C testing is indicated in patients: 1. With atypical muscle mass (e.g. Muscular Dystrophy, prolonged hospitalization or immobilization, amputation, malnourishment, body building (not taking rhGH), etc.) 2. On a high-protein diet and/or on creatine supplementation 3. With volatile serum creatinine levels and uncertainty in their GFR classification (e.g. classification G3a vs G3b) 4. Where there is analytical uncertainty in creatinine results (ie interference) Cystatin C testing is NOT indicated in the following 1. Patients with hypo- or hyperthyroidism 2. Patients with impaired kidney function and currently taking high-dose corticosteroids or recently tapered from a high dose 3. Patients with elevated levels of Growth Hormone Test Approval Requirements: Clinical Biochemist Approval Required F260-11-02 Biochemistry Approval for Test Referral Form THIS TEST WILL ONLY BE MADE AVAILABLE TO NEPHROLOGISTS AND ENDOCRINOLOGISTS FOR THE INDICATIONS LISTED ABOVE. |
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| Collection Devices: |
Lithium Heparin plasma is also acceptable.
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| Specimen Required: |
Serum: 1.0 mL
Pediatric Serum: 1.0 mL
Special Processing: Separate and freeze immediately. Store and ship frozen. Specimen Stability: Refrigerated: 7 days Frozen (-20°C or lower): Plasma (6 months), Serum (24 months) Other comments: Specimen is unsuitable for analysis if received thawed by the referral lab. |
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| Referral: |
Shipping & Storage: Store and ship frozen.
Referred Out Location: Specimens are referred out from HSC-MS5 to In-Common Laboratories (ICL)
Test ID: CYSTC Test Name: Cystatin C with Estimated Glomerular Filtration Rate (eGFR), Serum/Plasma ICL Test Menu Entry: https://iclabs.ca/test/606/
Testing Location: Children's Hospital Eastern Ontario (CHEO) 401 Smyth Road Ottawa ON K1H 8L1 |
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| Requisition: | |||||
| Reference Values: |
Reference Intervals:
Cystatin C: ≤ 1.20 mg/L CysC eGFR: ≥ 90 mL/min/1.73m2
Reference Value Document Links: https://iclabs.ca/test/606/ |
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| Availability: |
Within 2 Weeks
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| See Also: | |||||
| More Information: |
Interpretation & Assay Interferences: Report includes Cystatin C concentration and calculated eGFR.
For patients <18 years of age, eGFR will be calculated using the Schwartz Cystatin C Equation (Kidney Int. 2012. 82(4): 445-53).
For patients ≥18 years of age, eGFR will be calculated using the 2012 CKD-EPI Cystatin C Equation (NEJM. 2012. 367(1): 20-29). |