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Protocol - Cystatin C Assay for Kidney Function

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Description:

This protocol provides instructions for drawing, processing, and storing blood for the serum cystatin C assay according to the NHANES methods. Because there are no standard assays for cystatin C, the protocol also provides basic guidelines to aid comparability among different studies.

Protocol:

Exclusion Criteria

Persons will be excluded from this component if they:

Report that they have hemophilia; or

Report that they have received cancer chemotherapy in the last 4 weeks

SP = Sample Person.

1. Do you have hemophilia?

[ ] 1 Yes

[ ] 2 No

[ ] 7 Refused

[ ] 9 Don't Know

If the SP answers "Yes," the SP is excluded from the blood draw.

If the SP answers "No" or "Don't Know," blood is drawn from the SP.

2. Have you received cancer chemotherapy in the past four weeks or do you anticipate such therapy in the next four weeks?

[ ] 1 Yes

[ ] 2 No

[ ] 7 Refused

[ ] 9 Don't Know

If the SP answers "Yes," the SP is excluded from the blood draw.

If the SP answers "No" or "Don't Know," blood is drawn from the SP.

Venipuncture Procedures

Editor's Note: Please review chapter 4 of the Laboratory Procedures Manual from the National Health and Nutrition Examination Survey for a full description of Phlebotomy procedures: http://www.cdc.gov/nchs/data/nhanes/nhanes_07_08/manual_lab.pdf

Venipuncture should generally be performed using the median cubital, cephalic, or basilic veins in the left arm unless this arm is unsuitable. If the veins in the left arm are unsuitable, look for suitable veins on the right arm. If the veins in the antecubital space on both arms are not suitable, then look for veins in the forearm or dorsal side of the hand on the left arm/hand and then the right arm/hand.

Record the Results of the Venipuncture Procedure

Immediately after completing the venipuncture, record the results of the blood draw, the reasons for a tube not being drawn according to the protocol, and any comments about the venipuncture.

Process the Sample for the Cystatin C Assay

Editor's Note: Please review chapter 8 of the Laboratory Procedures Manual from the National Health and Nutrition Examination Survey 2007-2008 for a full description of Blood Processing procedures:

http://www.cdc.gov/nchs/data/nhanes/nhanes_07_08/manual_lab.pdf

Allow the blood to clot by setting aside for 30 to 45 minutes at room temperature. Do not clot for more than an hour.

Centrifuge the tube at room temperature to separate the serum and aliquot into an appropriate storage tube.

Determine if the serum is hemolyzed, turbid, lipemic, or icteric. If so, enter a comment to describe the plasma.

Laboratory Assay for Cystatin C

The Diabetes Working Group notes that although there is not a standardized assay, there are many different kits which are appropriate to measure the concentration of cystatin C in serum. Once an assay is chosen for a particular study, the Working Group recommends that no changes in the protocol be made over the course of the study.

Reference Ranges

Cystatin C ranges between 0.57 - 1.12 mg/L

Estimated Glomerular Filtration Rate:

estimated Glomerular Filtration Rate = 127.7 X Cystatin C -1.17 X Age -0.13 X [0.91 if Female] X [1.06 if African American]

Protocol Name from Source:

National Health and Nutrition Examination Survey (NHANES) Questionnaire. Laboratory Procedures Manual

Availability:

Publicly available

Personnel and Training Required

Phlebotomist

Laboratory that can perform the cystatin C assay.

Equipment Needs
Phlebotomy supplies
Requirements
Requirement CategoryRequired
Mode of Administration

Bioassay

Life Stage:

Participants:

6 years of age or older

Specific Instructions:
Selection Rationale

The National Health and Nutrition Examination Survey, produced by the Centers for Disease Control and Prevention's (CDC's) National Center for Health Statistics (NCHS), is one of the most widely used national surveys and was selected as the best practice methodology.

Language

Standards
StandardNameIDSource
Common Data Elements (CDE) Serum Cystatin-C Measurement Value in mg/L 3070913 CDE Browser
Process and Review

The Expert Review Panel (ERP) #1 reviewed the measures in the Anthropometrics, Diabetes, Physical Activity and Physical Fitness, and Nutrition and Dietary Supplements domains.

Guidance from the ERP includes:

  • Added recommendations on use of serum or plasma

    Previous version in Toolkit archive (link).

Source

Centers for Disease Control and Prevention (CDC), National Center for Health Statistics (NCHS), National Health and Nutrition Examination Survey Questionnaire, Laboratory Procedures Manual, 2007.

General References
Protocol ID:

250701

Variables:
Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
Research Domain Information
Measure Name:

Cystatin C Assay for Kidney Function

Release Date:

N/A

Definition

A bioassay to measure serum concentration of cystatin C, a protein that is filtered out of the blood by the kidneys.

Purpose

Cystatin C is a protein produced by the body. Cystatin C measurements can indicate kidney function problems and assess kidney disease. For the elderly, those who are overweight, and people who have a lot of muscle mass (e.g., body builders), Cystatin C-based estimates for glomerular filtration rate (eGFR) are believed to be less influenced by muscle mass or diet than creatinine-based estimates (National Kidney Foundation, 2015).This measurement of renal function is particularly important to old people with reduced muscle mass, which makes other assays less accurate.

Keywords

National Health and Nutrition Examination Survey, NHANES, Centers for Disease Control and Prevention, CDC, geriatrics, diabetes, kidney disease, sickle cell disease, reduced muscle mass, glomerular filtration rate, GFR, gerontology, aging, geriatrics