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CAUR
60157
CAS
parathyroid hormone-producing tumors, excess intake of vitamin D, or various malignancies. Nomograms
have been used to calculate ionized calcium from total calcium, albumin, and pH values. However,
calculated ionized calcium results have proven to be unsatisfactory. (A Mayo study of 114 patients found
significant differences between ionized and total calcium in 26% of patients.)
Useful For: Assessing calcium states during liver transplantation surgery, cardiopulmonary bypass, or
any procedure requiring rapid transfusion of whole blood in neonates and in critically ill patients Second
order test in the evaluation of patients with abnormal calcium values
Interpretation: Serum ionized calcium concentrations 50% below normal result in severely reduced
cardiac stroke work. With moderate to severe hypocalcemia, left ventricular function may be profoundly
depressed. Ionized calcium values are higher in children and young adults. Ionized calcium values vary
inversely with pH, approximately 0.2 mg/dL per 0.1 pH unit change.
Reference Values:
Males
or =20 years: 4.65-5.30 mg/dL
Females
or =18 years: 4.65-5.30 mg/dL
Clinical References: 1. Toffaletti JG: A clinical review of ionized calcium: a better indicator than
total calcium. Waltham, MA, Nova Biomedical, 1998 2. Tietz: Textbook of Clinical Chemistry and
Molecular Diagnostics, Fourth Edition, 2006. Measurement of free (ionized) Calcium; Effect of PH &
Anticoagulant.
Calcium, Random, Urine
Clinical Information: Calcium is the fifth most common element in the body. It is a fundamental
element necessary to form electrical gradients across membranes, an essential cofactor for many enzymes,
and the main constituent in bone. Under normal physiologic conditions, the concentration of calcium in
serum and in cells is tightly controlled. Calcium is excreted in both the urine and the feces.
Useful For: Identification of abnormal physiologic states causing excess or suppressed excretion of
calcium (such as hyperparathyroidism), vitamin D abnormality, diseases that destroy bone, prostate
cancer, and drug treatment (such as thiazide therapy)
Interpretation: Increased urinary excretion of calcium accompanies hyperparathyroidism, vitamin D
intoxication, diseases that destroy bone (such as multiple myeloma), metastasis from prostatic cancer, and
calcium supplementation. Patients with absorptive hypercalciuria (increased gut absorption) will have
lowered urine calcium with dietary restriction and, therefore, can be differentiated from patients with
hypercalciuria caused by hyperparathyroidism, hyperthyroidism, Paget disease, or "renal leak" type of
calciuria as seen in renal tubular acidosis. Thiazide drugs tend to reduce excretion of calcium. For
individuals consuming an average daily intake of 600 mg to 800 mg of calcium per day, the normal daily
excretion of calcium is: -25 mg to 300 mg for men -20 mg to 275 mg for women
Reference Values:
No established reference values
Clinical References: Bijvoet OLM: Kidney function in calcium and phosphate metabolism. In
Metabolic Bone Disease. Vol. 1. Edited by LV Avioli, SM Krane. New York, Academic Press, 1977, pp
49-140
Calcium, Total, Serum
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