Calcium, Urine (CA): CPT 82340

CPT Code: 

82340 

Specimen: 

Urine  

Volume:

25 mL 

Minimum Volume: 

1 mL 

Container:

Preferred:  Container with 10-20 mL of 6M HCl.  If preservatives are not used during 24 hour urine collection, acidify the sample to below pH 3.0 before analysis.

Methodology:

Spectrophotometry (SP)

Collection:

The test request form must state date and time collection started and date and time collection finished. State total volume.

Instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with patient's full name, room number, date and time collection started, and date and time collection finished. pH must be < 2.

Patient Preparation:

Urinary calcium results are more meaningful if the patient has been on a low calcium, neutral ash diet for three days prior to urine collection. Drugs affecting mineral metabolism should be withdrawn, if possible, two to four weeks prior to and during collection. These include antacids, phosphates, diuretics, glucocorticoids, carbonic anhydrase inhibitors, and anticonvulsants.

Reference Range:  

 Stability: 

Temperatures  Period 
Room Temperature  8 Hours 
Refrigerated (2-8 ⁰C)  2 Days 
Frozen (≤ 20 ⁰C)  Longer Storage 

 

Use: 

Calcium is the most important mineral in the body with approximately 98% found in the bones. The calcium in the blood is necessary for many important bodily functions, including muscle contraction, blood clotting, bone formation, conduction of nerve impulses, and parathyroid gland activity. Urinary calcium reflects dietary intake, rate of calcium absorption by the intestine and bone resorption. Urinary calcium is used primarily to evaluate parathyroid function and the effects of vitamin D. 

Clinical Significance:  High Calcium levels are mostly found in individuals who suffer from hyperparathyroidism.  However, there are other clinical entities that may be associated with increased urine calcium: Sarcoidosis, Paget's disease of bone, vitamin D intoxication, hyperthyroidism and glucocorticoid excess.

Low Calcium in urine calcium is seen with thiazide diuretics, vitamin D deficiency and familial hypocalciuric hypercalcemia.

 

Causes for Rejection: 

Improper labeling 

Limitations: 

Oral contraceptive use may depress results. Requires accurate 24-hour urine collection. 

Interfering Substances: Interference due to magnesium is negligible at magnesium levels normally encountered in human serum.  A maximum positive interference of 0.7 mg/dL occurs at a magnesium level of 7 mg/dL. Calcium values may be falsely decreased in the presence of gadolinium-containing contrast agents such as Omniscan.  Therefore it is recommended to avoid drawing samples for serum calcium determination 24 hours after administration of Omniscan.

Bilirubin (unconjugated) of 80mg/dL decreases calcium at 6.4mg/dL by 11%.

Lipemia of 600mg/dL and above tripped a test report message; therefore the magnitude of the interference could not be determined.