Test Catalog

Test Id : CSTCE

Cystatin C with Estimated Glomerular Filtration Rate (eGFR), Serum

Useful For
Suggests clinical disorders or settings where the test may be helpful

Assessing kidney function in patients suspected of having kidney disease

 

Monitoring treatment response in patients with kidney disease

 

An index of glomerular filtration rate (GFR), especially in patients where serum creatinine may be misleading (eg, very obese, older adults, or malnourished patients)

 

Calculation of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) cystatin C estimated GFR for patients where serum creatinine may be misleading (eg, very obese, older adults, or malnourished patients)

Method Name
A short description of the method used to perform the test

Immunoturbidimetric

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Cystatin C with Estimated GFR, S

Specimen Type
Describes the specimen type validated for testing

Serum

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and serum aliquoted into a plastic vial within 2 hours of collection.

Forms

If not ordering electronically, complete, print, and send one of the following forms with the specimen:

-Cardiovascular Test Request Form (T724) with the specimen.

-Renal Diagnostics Test Request (T830)

-General Test Request (T239)

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.25 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia OK
Gross icterus Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 30 days
Ambient 7 days

Useful For
Suggests clinical disorders or settings where the test may be helpful

Assessing kidney function in patients suspected of having kidney disease

 

Monitoring treatment response in patients with kidney disease

 

An index of glomerular filtration rate (GFR), especially in patients where serum creatinine may be misleading (eg, very obese, older adults, or malnourished patients)

 

Calculation of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) cystatin C estimated GFR for patients where serum creatinine may be misleading (eg, very obese, older adults, or malnourished patients)

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Cystatin C is a low-molecular weight (13,250 Da) 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); ie, a high concentration indicates a low GFR, while a lower concentration indicates a higher GFR, similar to creatinine.

 

The renal handling of cystatin C differs from creatinine. While both are freely filtered by glomeruli, once filtered, cystatin C, unlike creatinine, is reabsorbed and metabolized by proximal renal tubules. Therefore, under normal conditions, cystatin C does not enter the final excreted urine to any significant degree.

 

The serum concentration of cystatin C is not greatly affected by body mass, age, sex, or race. Thus, in certain cases, cystatin C may be a more reliable marker of kidney function (ie, GFR) than creatinine.

 

GFR can be estimated (eGFR) from serum cystatin C utilizing an equation that includes the age and sex of the patient. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) cystatin C equation was developed by Inker et al(1) 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 whose muscle mass is abnormally high or low (for example quadriplegics, much older adults, 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 (eg, amongst hospitalized individuals).(2)

 

The same group also developed an eGFR equation that uses serum creatinine and cystatin C, in addition to age, sex, and race.(1) This equation may be useful to average out potential confounders of creatinine versus cystatin C.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

CYSTATIN C:

18-49 years: 0.63-1.03 mg/L

> or =50 years: 0.67-1.21 mg/L

0-17 years: Reference values have not been established. Refer to estimated glomerular filtration rate (eGFR).

 

ESTIMATED GFR:

>60 mL/min/BSA (body surface area)

Adult eGFR: Estimated GFR calculated using CKD-EPI Cystatin C equation.(1)

Pediatric eGFR: Estimated GFR calculated using Schwartz Cystatin C equation.(1)

Interpretation
Provides information to assist in interpretation of the test results

Cystatin C:

Cystatin C inversely correlates with the glomerular filtration rate (GFR), that is, elevated levels of cystatin C indicate decreased GFR. Cystatin C may provide more accurate assessment of GFR for very obese, older adults, or malnourished patients than creatinine. Cystatin C equation does not require patient ethnic data and can be used for those patients with this information unavailable.

 

Due to immaturity of kidney function, cystatin C levels are higher in neonates less than 3 months of age.(3)

 

Estimated GFR:

Chronic kidney disease (CKD) is defined as the presence of persistent and usually progressive reduction in GFR (GFR <60 mL/min/1.73 m[2]) and/or albuminuria (>30 mg of urinary albumin per gram of urinary creatinine), regardless of GFR.

 

According to the National Kidney Foundation Kidney Disease Outcome Quality Initiative (KDOQI) classification, among patients with CKD, irrespective of diagnosis, the stage of disease should be assigned based on the level of kidney function.(4)

 

Table. Kidney Disease: Improving Global Outcomes (KDIGO) guidelines provide the following GFR categories

 

Stage

Description

GFR mL/min/BSA

1

Kidney damage with normal or increased GFR

90

2

Kidney damage with mild decrease in GFR

60-89

3A

Mild to moderate decrease in GFR

45-59

3B

Moderate to severe decrease in GFR

30-44

4

Severe decrease in GFR

15-29

5

Kidney failure

<15 (or dialysis)

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The estimated glomerular filtration rate (eGFR) is not a precise measure of GFR and can be influenced by nonrenal factors such as inflammation.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Inker LA, Schmid CH, Tighiouart H, et al; CKD-EPI Investigators: Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012 Jul;367(1):20-29. doi: 10.1056/NEJMoa1114248

2. Frazee E, Rule AD, Lieske JC, et al: Cystatin C-guided vancomycin dosing in critically ill patients: a quality improvement project. Am J Kidney Dis. 2017 May;69(5):658-666. doi: 10.1053/j.ajkd.2016.11.016

3. Buehrig CK, Larson TS, Bergert JH, et al: Cystatin C is superior to serum creatinine for the assessment of renal function. J Am Soc Nephrol. 2001;12:194A

4. Inker LA, Astor BC, Fox CH, et al: KDOQI US commentary on the 2012 KDIGO Clinical Practice Guideline for the Evaluation and Management of CKD. Am J Kidney Dis. 2014 May;63(5):713-735. doi: 10.1053/j.ajkd.2014.01.416

5. Grubb AO: Cystatin C--properties and use as a diagnostic marker. Adv Clin Chem. 2000;35:63-99. doi: 10.1016/s0065-2423(01)35015-1

6. 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. doi: 10.1053/ajkd.2000.8237

7. Larsson A, Hansson LO, Flodin M, Katz R, Shlipak MG: Calibration of the Siemens cystatin C immunoassay has changed over time. Clin Chem. 2011 May;57(5):777-778. doi: 10.1373/clinchem.2010.159848

8. Voskoboev NV, Larson TS, Rule AD, Lieske JC: Importance of cystatin C assay standardization. Clin Chem. 2011 Aug;57(8):1209-1211. doi: 10.1373/clinchem.2011.164798

9. Nitsch D, Sandling JK, Byberg L et al: Fetal, developmental, and parental influences on cystatin C in childhood: the Uppsala Family Study. Am J Kidney Dis. 2011 Jun;57(6):863-872. doi: 10.1053/j.ajkd.2010.12.025

10. Voskoboev NV, Larson TS, Rule AD, Lieske JC: Analytic and clinical validation of a standardized cystatin C particle enhanced turbidimetric assay (PETIA) to estimate glomerular filtration rate. Clin Chem Lab Med. 2012 Mar;50(9):1591-1596. doi: 10.1515/cclm-2012-0063

11. Finney H, Newman DJ, Thakkar H, Fell JM, Price CP: Reference ranges for the plasma cystatin C and creatinine measurements in premature infants, neonates, and older children. Arch Dis Child. 2000 Jan;82(1):71-75. doi: 10.1136/adc.82.1.71

12. Schwartz GJ, Schneider MF, Maier PS, et al: Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C. Kidney Int. 2012 Aug;82(4):445-453. doi: 10.1038/ki.2012.169

Method Description
Describes how the test is performed and provides a method-specific reference

Cystatin C:

Serum samples from patients are mixed with latex particles coated with anti-cystatin C antibodies. Human cystatin C agglutinates with latex particles coated with the anti-cystatin C antibodies. The aggregate is determined turbidimetrically at 546 nm.(Package insert: Tina-quant Cystatin C Gen.2. Roche Diagnostics; 01/2017)

 

Estimated GFR is calculated in the laboratory information system, SCC Soft, 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 (Salvador CL, Tondel C, Rowe AD, et al: Estimating glomerular filtration rate in children: evaluation of creatinine- and cystatin C-based equations. Pediatr Nephrol. 2019 Feb;34(2):301-311. doi: 10.1007/s00467-018-4067-3; Inker LA, Schmid CH, Tighiouart H, CKD-EPI Investigators, et al: Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012 Jul;367(1):20-29; National Kidney Foundation: CKD-EPI Cystatin C Equation (2012). Accessed March 25, 2021. Available at: www.kidney.org/content/ckd-epi-cystatin-c-equation-2012)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

82610

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
CSTCE Cystatin C with Estimated GFR, S 87430-5
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
GFRC eGFR by Cystatin C 50210-4
CSTNC Cystatin C, S 33863-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports