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CPT:
82610
Synonyms
- Cystatin C
- eGFR
- Estimated Glomerular Filtration Rate
- GFR, Estimated
Test Includes
Cystatin C; eGFR calculation
Expected Turnaround Time
2 - 5 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Documents
Specimen Requirements
Specimen
Serum or plasma
Volume
0.5 mL
Minimum Volume
0.2 mL
Container
Red-top tube, gel-barrier tube, or green-top (heparin) tube
Collection
Separate serum or plasma from red blood cells.
Storage Instructions
Room temperature
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Patient Preparation
Overnight fasting is preferred.
Causes for Rejection
Specimen other than serum or heparinized plasma; grossly hemolyzed (>1,000 mg/dL Hgb) samples; excessive turbidity and clots in samples
Test Details
Use
Since it is formed at a constant rate and freely filtered by the healthy kidney, cystatin C is a good marker of renal function. Serum concentrations of cystatin C are almost totally dependent on glomerular filtration rate (GFR). A reduction in GFR causes a rise in the concentration of cystatin C.1,2
Can be used as a confirmatory test for the diagnosis of chronic kidney disease (CKD) in patients with a decreased GFR as estimated from creatinine.
Data suggests that 3.6% of U.S. adults would be classified as having CKD solely on the basis of a creatinine-based GFR estimate of 45 to 59 mL per minute per 1.73m2. A strategy of measuring cystatin C when the creatinine-based estimate is in this range and then reestimating GFR with the use of both these markers could correctly reclassify a substantial proportion of such patients as not having CKD and not being at high risk.
Can also be used to screen for CKD among persons who have a creatinine-based GFR estimate of 60 to 74 mL per minute per 1.73m2 without albuminuria (10.9% of US adults) or to obtain a more accurate estimation of GFR in patients with muscle wasting or chronic illness.
Limitations
Cystatin C has not been shown to be affected by factors such as muscle mass and nutrition, factors which have been demonstrated to affect creatinine values. In addition, a rise in creatinine does not become evident until the GFR has fallen by approximately 50%.
Methodology
Turbidimetric (directly traceable to ERM-DA471/IFCC, the international standard reference material)
Additional Information
The estimated glomerular filtration (GFR) provides an assessment of the filtering capacity of the kidney. The eGFR is calculated from a serum cystatin C using the CKD-EPI equation, 2012.3
Footnotes
1. Grubb A. Diagnostic value of analysis of cystatin C and protein HC in biological fluids. Clin Nephrol. 1992;38 Suppl 1: S20-7.1284235
2. Coll E, Botey A, Alvarez L, et al. Serum cystatin C as a new marker for noninvasive estimation of glomerular filtration rate and as a marker for early renal impairment. Am J Kidney Dis. 2000 Jul;36(1):29-34.10873868
3. National Kidney Foundation. CKD-EPI Cystatin C Equation (2012). National Kidney Foundation web site. https://www.kidney.org/content/ckd-epi-cystatin-c-equation-2012. Accessed December 2020.
References
Grubb A, Blirup-Jensen S, Lindstrom V, et al. First certified reference material for cystatin C in human serum ERM- DA471/IFCC. Clin Chem Lab Med. 2010 Nov;48(11):1619-1621.21034257
Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012 Jul 5;367(1):20-29.22762315
Peralta CA, Katz R, Sarnak MJ, et al. Cystatin C identifies chronic kidney disease patients at higher risk for complications. J Am Soc Nephrol. 2011 Jan;22(1):147-155.21164029
Peralta CA, Shlipak MG, Judd S, et al. Detection of chronic kidney disease with creatinine, cystatin C, and urine albumin-to-creatinine ratio and association with progression to end-stage renal disease and mortality. JAMA. 2011 Apr 20;305:1545-1552.21482744
Stevens LA, Padala S, Levey AS. Advances in glomerular filtration rate-estimating equations. Curr Opin Nephrol Hypertens. 2010 May;19(3):298-307.20393287
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 121265 | Cystatin C with eGFR | 87430-5 | 121252 | Cystatin C | mg/L | 33863-2 |
| 121265 | Cystatin C with eGFR | 87430-5 | 121266 | eGFR | mL/min/1.73 | 50210-4 |
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