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.
Serum or plasma
1 mL
0.5 mL
Red-top tube, gel-barrier tube, or green-top (heparin) tube
Separate serum or plasma from red blood cells.
Room temperature
Temperature
Period
14 days
Refrigerated
Frozen
Freeze/thaw cycles
Stable x3
Specimen other than serum or heparinized plasma; grossly hemolyzed (>1,000 mg/dL Hgb) samples; excessive turbidity and clots in samples
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.
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%.
Immunologic
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
