Calcium, 24-Hour Urine (with Creatinine) [1635X]

Message

TESTS CAN BE ORDERED SEPERATELY AND COMPLETED IN-HOUSE (UCA24HR & UCREA24HR), UNLESS THE DR IS REQUESTING THE RATIO.

Test Code

15830

Alias/See Also

Calcium-Creatinine Ratio, 24-Hour
NG000080

CPT Codes
82340, 82570

Includes

CPT code 81050 may be added at an additional charge for volume measurement

Preferred Specimen

10 mL aliquot of a well-mixed preserved 24-hour urine collection in (25 mL of 6N HCl) submitted in a plastic leak-proof container

Minimum Volume

2 mL

Other Acceptable Specimens

Unpreserved 24-hour urine collected in a plastic leak-proof container • Urinalysis transport tube (yellow-top, blue fill line, preservative tube)

Instructions

Collect urine with 25 mL of 6N HCl to maintain a pH below 3. It is acceptable to add preservative after collection if urine is refrigerated during collection. Adjust pH to <3.0 Record total volume an collection time on specimen container and requisition. Aliquot urine specimens and send at room temperature to the laboratory.

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 5 days
Refrigerated: 35 days
Frozen: 6 months

Methodology
Spectrophotometry (SP)

Setup Schedule

Set up: Daily; Report available: Next day

Limitations

Oral contraceptive use may depress results.

Reference Range

Unrestricted Calcium Diet

Male	55-300 mg/24 h
Female	35-250 mg/24 h

Restricted Calcium Diet

Male	55-200 mg/24 h
Female	35-200 mg/24 h

Calcium/Creatinine Ratio

Male	30-210 mg/g creat
Female	30-275 mg/g creat

Creatinine, 24-Hour Urine

<3 Years	Not established
3-8 Years	0.10-0.80 g/24 h
9-12 Years	0.20-1.40 g/24 h
13-17 Years	0.40-1.90 g/24 h
>17 Years	0.50-2.15 g/24 h

Clinical Significance

This quantitative test, performed with a 24-hour urine specimen, may help screen for hypercalciuria, one of the established risk factors for kidney stone formation [1-3]. This test may also help assess metabolic disorders of calcium metabolism, such as hyperparathyroidism, bone disease, and idiopathic hypercalciuria. In general, 24-hour urine specimens are preferred to random urine specimens when measuring calcium for diagnostic evaluation of hypercalciuria [1].

Calcium is essential for bone formation and nerve, muscle, and heart functions. Calcium metabolism is jointly regulated by parathyroid hormone and vitamin D metabolites. Urinary calcium excretion is the major route of calcium elimination and reflects kidney tubular filtration and reabsorption of calcium in addition to dietary intake, intestinal absorption, and bone resorption [2]. Creatinine excretion is useful in determining whether 24-hour urine specimens for calcium have been completely and accurately collected because daily urine excretion of creatinine generally shows minimal fluctuation [2].

Urinary calcium levels may be elevated in patients with idiopathic hypercalciuria, chronic kidney disease, hyperparathyroidism, vitamin D intoxication, Paget disease of bone, sarcoidosis, or conditions that infiltrate and destroy bones (eg, multiple myeloma and a variety of metastatic cancers) [2,3]. Urinary calcium levels may be decreased in patients with hypoparathyroidism, vitamin D deficiency rickets, osteomalacia, or familial hypocalciuric hypercalcemia [2,3].

A calcium/creatinine clearance ratio, calculated from 24-hour urinary calcium and creatinine concentrations and total serum calcium and creatinine concentrations may help differentiate primary hyperparathyroidism (PHPT) from familial hypocalciuric hypercalcemia (FHH) [4].

Note that use of calcium supplements and loop diuretics may cause increased urinary calcium levels; thiazide diuretics may cause decreased urinary calcium levels [3].

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

References
1. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
2. Rifai N, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elservier Inc; 2022
3. MedlinePlus [Internet]. Calcium-urine. Accessed September 1, 2022. https://medlineplus.gov/ency/article/003603.htm
4. Arshad MF, et al. Postgrad Med J. 2021;97(1151):577-582.

Performing Laboratory

Quest Diagnostics Nichols Institute

14225 Newbrook Drive

Chantilly, VA 20153

Last Updated: March 17, 2023

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.