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Test Code CYSC Cystatin C with Estimated GFR

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Li-Heparin Mint Green Top

Other Acceptable specimens: Serum/Gold Top, Serum/Red Top

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent room temperature at 15-25oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours.

Reference Values

 

Test

Age

Sex

Reference Range
Cystatin C 0 - 17 years ALL None
Cystatin C 18 - 49 years ALL 0.63 - 1.03 mg/dL
Cystatin C ≥50 years ALL 0.67 - 1.21 mg/dL

      Note: Cystatin C reference range based on literature review. 

There is no established reference eGFR by Cystatin C.

 

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

CPT Codes

82610

LOINC Codes

87430-5 (Cystatin C with Estimated GFR)

  • 33863-2 (Cystatin C)
  • 50210-4 (eGFR by Cystatin C)

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL

Specimen Stability

Storage Temperature

Stability

Room temperature

7 days

Refrigerated

7 days

Frozen

6 months

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Test Components

Cystatin C

Glomerular Filtration Rate (eGFR)

Clinical Indications

  • Serum creatinine is the most commonly used marker for estimation of GFR. However, it has become evident that the creatinine concentration is far from ideal because it is significantly changed by other factors such as muscle mass, diet, gender, age and tubular secretion.
  • Cystatin C is a low-molecular weight protease inhibitor that is constitutively expressed by all nucleated cells and freely filtered by the kidneys. Serum/plasma concentrations of Cystatin C is inversely correlated with GFR.
  • Cystatin C in plasma and serum has been proposed as a more sensitive marker for GFR in children and adults, and several studies, as well as one meta analysis, have suggested that cystatin C is superior to serum creatinine for estimation of GFR.

Methodology

Particle enhanced immunoturbidimetric assay. (Roche Diagnostics)

Additional Information

  • Results should always be assessed in conjunction with patient's medical history, clinical examination and other findings.
  • Cystatin C-based estimated GFR is calculated using the Schwartz Cystatin C equation for patients under 18 years old and the CKD-EPI Cystatin C Equation (2012) for patients 18 years of age and older.

           (https://www.kidney.org/ckd-epi-cystatin-c-equation-2012)

  • Salvador CL, et al. Estimating glomerular filtration rate in children: evaluation of creatinine- and cystatin C-based equations. Pediatr Nephrol. 2019 Feb;34(2):301-311.
  • Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012;367(1):20-29.
  •  eGFR Calculations:

             CKD-EPI Cystatin C equation (2012) for estimating GFR for Adults (≥18 years of age):

                 eGFR = 133 x min(Scys/0.8, 1)^-0.499 x max (Scys/0.8, 1)^-1.328 x 0.996^Age x 0.932 [if female]

                 eGFR (estimated glomerular filtration rate) = mL/min/1.73 m^2

                 Scys (standardized serum cystatin C) = mg/L

                 min = indicates the minimum of Scys/0.8 or 1

                 max = indicates the maximum of Scys/0.8 or 1

                 age = years

            Schwartz Cystatin C equation for Pediatrics (<18 years of age):

                eGFR = 70.69 x  (Scys)^-0.931

               Scys (standardized serum cystatin C) = mg/L

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: 4 hours

Testing Schedule: 24/7

Synonyms/Keyword Search

CYSC, cystatin, eGFR, GFREA, GFRE

Last Review Date

10/3/24