Test Details
Methodology
Turbidimetric (directly traceable to ERM-DA471/IFCC, the international standard reference material)
Result Turnaround Time
3 - 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.
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).1,2 A reduction in GFR causes a rise in the concentration of cystatin C.
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%.
Footnotes
Specimen Requirements
Specimen
Serum (preferred) or plasma
Volume
1 mL
Minimum Volume
0.5 mL
Container
Gel-barrier tube or green-top (heparin) tube
Collection Instructions
If green-top (heparin) tube is used, separate plasma from red blood cells and transfer plasma to a transfer tube.
Stability Requirements
| Temperature | Period |
|---|---|
| Room temperature | 7 days at 15°C to 25°C (stability provided by manufacturer or literature reference) |
| Refrigerated | 7 days at 2°C to 8°C (stability provided by manufacturer or literature reference) |
| Frozen | 6 months at -20°C (stability provided by manufacturer or literature reference) |
| Freeze/thaw cycles | Stable x1 (stability provided by manufacturer or literature reference) |
Reference Range
See table.
| Age | Range (mg/L) |
|---|---|
| 0 to 1 y | Not established |
| 2 to 50 y | 0.60−1.00 |
| 51 to 60 y | 0.67−1.14 |
| 61 to 70 y | 0.72−1.16 |
| 71 to 80 y | 0.78–1.15 |
| >80 y | 0.87–1.12 |
Storage Instructions
Room temperature
Causes for Rejection
Specimen other than serum or heparinized plasma; grossly hemolyzed (>1,000 mg/dL Hgb) samples; excessive turbidity and clots in samples
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 121251 | Cystatin C | 33863-2 | 121252 | Cystatin C | mg/L | 33863-2 |
| Order Code | 121251 | |||||
| Order Code Name | Cystatin C | |||||
| Order Loinc | 33863-2 | |||||
| Result Code | 121252 | |||||
| Result Code Name | Cystatin C | |||||
| UofM | mg/L | |||||
| Result LOINC | 33863-2 |