Home
HelpCatalog ID CYST C Cystatin C with estimated GFR
Specimen Type
Gold top serum separator tube (serum) preferred
Red top tube acceptable
Summary
The non-glycosylated basic protein, cystatin C, is produced at a constant rate in nearly every nucleated cell in the human body. It is freely filtered through a normal Glomerular membrane, and is then reabsorbed and almost entirely catabolized in the proximal tubules. Hence, the cystatin C concentration in human blood is closely related to glomerular filtration rate (GFR) [2]. A reduction in the GFR causes a rise in the concentration of cystatin C. The cystatin C concentration has not been shown to be significantly influenced by other factors such as muscular mass, inflammatory diseases, sex, age, or diet.
Storage and Transport
Stable for 26 days at room temperature (8 - 25C) or refrigerated (2 - 8C)
Reference Values
cystatin C: 0.47 - 1.03 mg/L
cyst C (estimated) GFR: 0 - 90 mg/min/1.73m2
(Unable to report Cystatin C GFR when the Cystatin C level is <0.25 mg/L or >8.28 mg/L)
Causes for Rejection
wrong sample type, insufficient quantity
Performing Lab
Core Lab, AD 3301, 706-721-2120
Additional Information
For calculation of GFR from cystatin C values measured with the Gentian assay the following prediction equation is recommended using mg/L as the unit factor:
The equation is valid for persons above 14 years of age.
GFR [mL/min/1.73 m2] = 79.901 / Cystatin C [mg/L]1.438
NOTE: It should be noted that there are different formulas based on different cystatin C assays. Use of these alternate formulas may reveal inaccurate GFR results if an inappropriate combination of formula and assay is used.