Creatine, 24-Hour Urine

CPT: 82540
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Special Instructions

State patient's sex and 24-hour total urine volume on the request form.


Expected Turnaround Time

3 - 6 days


Related Information


Related Documents


Specimen Requirements


Specimen

Urine (24-hour), frozen


Volume

2 mL aliquot


Minimum Volume

0.2 mL aliquot (Note: This volume does not allow for repeat testing.)


Container

Plastic urine container, no preservative


Collection

Instruct the patient to void at 8 AM and discard the specimen. Then collect all the urine, including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Measure and record on the test request form the 24-hour total volume. Mix well. Transfer the urine into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp N° 49482). Label the container with the patient's name, date, and time collection started and finished. The specimen should be frozen immediately and maintained frozen until tested.


Storage Instructions

Freeze


Causes for Rejection

Thawed specimen; 6N HCl, boric acid, or alkali added to collection (Acid or alkali preservative will convert creatine to creatinine, falsely lowering creatine values.)


Test Details


Use

Determine creatinuria; increased urine creatine values may be obtained from diseases that reduce muscle mass, including fasting, muscular dystrophy, poliomyelitis, atrophy, inflammatory destructive muscle disease as polymyositis, hyperthyroidism, as well as corticosteroid induced myopathy.


Methodology

Enzymatic (creatinase)/spectrophotometry


Reference Interval

Male: 0−40 mg/24 hours; female: 0−80 mg/24 hours


Additional Information

Creatine is endogenously synthesized in the kidney, liver, and pancreas. It is transported in blood to other organs such as muscle and brain, where it is phosphorylated to phosphocreatine. Interconversion of phosphocreatine and creatine is a unique feature of the metabolic processes of muscle contraction; some of the free creatine in muscle spontaneously converts to creatinine, its anhydride. Between 1% and 2% of muscle creatine is converted to creatinine daily.


LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
003475 Creatine, 24-Hour Urine 003477 Creatine,U,mg/dL mg/dL 2149-3
003475 Creatine, 24-Hour Urine 003476 Creatine,24-hr Ur mg/24 hr 2150-1

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