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Creatinine Clearance
Test Code7943
Preferred Specimen
10 mL 24-hr urine (well mixed, unpreserved) collected in 24-hour urine container and
1 mL serum
1 mL serum
Minimum Volume
Serum and Plasma: 0.5 mL • 24-hr urine (well mixed, unpreserved) and Acid urine: 0.5 mL
Other Acceptable Specimens
Urinalysis transport tube (yellow-top, blue fill line, preservative tube) • 1 mL plasma collected in sodium heparin (green-top) or lithium heparin (green-top) tube
Instructions
Record total volume and collection time on specimen container and requisition. Indicate the patients height (in feet and inches) and weight (in lbs.) on the test requisition.
Note: A serum creatinine level must be collected within 24 hours of the beginning or ending of the urine collection.
Note: A serum creatinine level must be collected within 24 hours of the beginning or ending of the urine collection.
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Refrigerated: 7 days
Frozen: 28 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Grossly icteric • Anticoagulants other than heparin
Methodology
Spectrophotometry
Clinical Significance
Creatinine clearance is used to evaluate the glomerular filtration rate (GFR). Clearance is defined as that volume of plasma from which a measured amount of substance could be completely eliminated into the urine per unit of time. Daily creatinine production is fairly constant except when there is massive injury to muscle.
