calcium (Ca+2) in 24 hour urine
Indications
- evaluation of urinary calculus
- evaluation of hyperparathyroidism
- evaluation of renal osteodystrophy
Reference interval
- 100-250 mg/24 hours
- > 300 mg/day in men, 250 mg/day in women or > 4 mg/kg/24 hours is significantly elevated
Principle
Calcium is the fifth most abundant mineral element in the human body. Approximately 98% of the calcium in an adult is present in the skeleton, but calcium also plays a vital role in blood coagulation, neuromuscular conduction, maintenance of normal tone, and excitability of skeletal & cardiac muscle. Calcium is also involved in the glandular synthesis & regulation of exocrine & endocrine glands; preservation of cell membrane integrity & permeability, particularly in terms of sodium & potassium exchange; the process of vision; & complex intracellular events involving the calcium-binding protein calmodulin. The major net loss of calcium is urinary excretion, which accounts for 50 to 200 mg or more each day, depending on dietary intake. In the calcium method for the ACA analyzer, calcium reacts with calcium o- cresolphthalein complexone (OCPC) to form a purple complex. The amount of complex thus formed is proportional to the calcium concentration & is measured using a two filter (577-600) end- point technique. Magnesium ions, which also form a colored complex with OCPC are removed from the reaction by complexation with 8-quinilinol.
Clinical significance
The major net loss of calcium is urinary excretion, which accounts for 50 to 200 mg or more each day, depending on dietary intake. Urinary calcium excretion is enhanced by hypercalcemia, phosphate deprivation, acidosis, & glucocorticoids. Urinary calcium excretion is diminished by parathyroid hormone, certain diuretics, and probably vitamin D.
Increases
Specimen
2 mL aliquot of a 24-hour urine collection. Proper 24 hour urine collection procedure should be followed, & collection container should be refrigerated at 2-6 degrees C during collection. Upon receipt in the work area, it should be well-mixed & measured in a graduated cylinder. The total volume should be recorded. Mix 10 mL of well-mixed urine with 0.1 mL concentrated HCL (or some multiple thereof). The sample should be analyzed within three days.
More general terms
Additional terms
References
- ↑ Kaplan, Lawrence A. & Pesce, Amadeo J., Clinical Chemistry: Theory, Analysis, & Correlation, 2nd Edition, The C.V. Mosby Company, St. Louis, MO, 1989, pp.350, 865-868.
- ↑ Henry, John Bernard, M.D., Clinical Diagnosis & Management by Laboratory Methods, 18th Edition, W.B. Saunders Company, Philadelphia, PA, 1991, pp. 152-165.
- ↑ ACA IV Discrete Clinical Chemistry Analyzer Instrument Manual, Volume 3A, Chapter 6: Test Methodology, CALCM 7.
- ↑ Medline Plus: Calcium - urine http://www.nlm.nih.gov/medlineplus/ency/article/003603.htm
- ↑ Calcium, urine Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0020472.jsp
- ↑ Panel of 8 tests Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0020472.jsp
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