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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Calcium, 24-Hour Urine (with Creatinine) [1635X]
Test CodeCPT Codes
82340, 82570
Includes
Preferred Specimen
Minimum Volume
Other Acceptable Specimens
Instructions
Transport Temperature
Room temperature
Specimen Stability
Refrigerated: 35 days
Frozen: 6 months
Methodology
Spectrophotometry (SP)
Setup Schedule
Set up: Daily; Report available: Next day
Limitations
Reference Range
Male | 55-300 mg/24 h | |
Female | 35-250 mg/24 h |
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.