Creatinine, serum; eGFR calculation
Within 1 day
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 (preferred) or plasma
1 mL
0.7 mL (Note: This volume does not allow for repeat testing.)
Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube. Do not use oxalate, EDTA, or citrate plasma.
Separate serum or plasma from cells within 45 minutes of collection.
Maintain specimen at room temperature.1
Temperature
Period
Room temperature
14 days
Refrigerated
Frozen
Freeze/thaw cycles
Stable x3
Hemolysis; improper labeling
A renal function test used in eGFR calculation.2
High creatinine: Renal diseases and insufficiency with decreased glomerular filtration, urinary tract obstruction, reduced renal blood flow including congestive heart failure, shock, and dehydration; rhabdomyolysis can cause elevated serum creatinine. Low creatinine: Small stature, debilitation, decreased muscle mass; some complex cases of severe hepatic disease can cause low serum creatinine levels. In advanced liver disease, low creatinine may result from decreased hepatic production of creatinine and inadequate dietary protein as well as reduced muscle mass.3
With reduced renal blood flow, creatinine rises less quickly than urea nitrogen. Concentration of creatinine only becomes abnormal when about half or more of the nephrons have stopped functioning in chronic progressive renal disease. Antibiotics containing cephalosporin lead to significant false-positive values if samples are drawn within four hours of a dose.4 With severe renal disease, creatinine is not reliable in the presence of cefoxitin therapy. There is less interference reported from the cephalosporins cephalothin, cephaloridine, cephadrine sodium, and cephaloglycin dihydrate. Lipemia, hemolysis, and bilirubin may interfere.5,6
Interfering Endogenous Substances7
Deviations
Degree of Interference
Pyruvate (serum/plasma)
>2.6 mg/dL
+12.8%
Glucose (serum/plasma)
>450 mg/dL
+16%
Ascorbic acid (serum/plasma)
>88 mg/dL
-10.1%
Urea (urine)
>12612 mg/dL
-11.0%
Kinetic Jaffe
See table.
Age
Female* (mg/dL)
Male (mg/dL)
*LabCorp internal studies.
Age/sex regardless
0.57-1.00
0.76-1.27
<2 m
0.44-1.19
2 to 11 m
0.17-1.18
1 to <3 y
0.19-0.42
3 to <5 y
0.26-0.51
5 to <7 y
0.30-0.59
7 to <9 y
0.37-0.62
9 to <11 y
0.39-0.70
11 to <13 y
0.42-0.75
13 to <15 y
0.49-0.90
=15 y
