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Insource Diagnostics


Alternative Names
  • Ca (Calcium)
  • Calcium (Ca)
  • Calcium
  • Total

Test Code: 4525

CPT: 82310
Tests Included Calcium
Use Measurement of calcium is used in the diagnosis and treatment of parathyroid disease, a variety of bone diseases, chronic renal disease and tetany (intermittent muscular contractions or spasms). Calcium levels may also reflect abnormal vitamin D or protein levels.
Clinical Utility Although more than 99% of body calcium exists in bones and teeth, it is the calcium in blood which is of most concern clinically. The bones serve as a reservoir to maintain relative constancy of serum calcium by releasing calcium when required to prevent hypocalcemia and trapping calcium to prevent excessively high levels of serum calcium. The uptake and release of calcium from bone is under the control of parathyroid hormone, vitamin D, calcitonin and adrenal cortical steroids.2 Calcium ions are important in the transmission of nerve impulses, as a cofactor in several enzyme reactions, in the maintenance of normal muscle contractility, and in the process of coagulation.

A significant reduction in calcium ion concentration in blood results in muscle tetany.Impaired function of the parathyroid glands or impaired vitamin-D synthesis can also lead to low caclium values. Chronic renal failure is also frequently associated with hypocalcemia due to decreased vitamin-D synthesis as well as hyperphosphatemia and skeletal resistance to the action of parathyroid hormone (PTH). A characteristic symptom of hypocalcemia is latent or manifest tetany and osteomalacia.3

A higher than normal concentration of calcium ions produces lowered neuromuscular excitability and muscle weakness along with other more complex symptoms. Often, the primary cause is hyperparathyroidism (pHPT) or bone metastasis of carcinoma of the breast, prostate, thyroid gland, or lung.4
Intended Patient Population 18+ and Older Adult Males & Females
Patient Preparation None Specified
Sample Serum, Plasma
Tube Red, Green, Tiger 
Volume 4mL Whole Blood (1mL Serum/Plasma)
Min Sample Volume 0.1 mLs
Reference Ranges M & F ≥ 18 yrs old; 8.6-10.3 mg/dL
Analytical Measurement Range 5-20 mg/dL
Critical Values ≤ 6.5 ≥ 13.0 mg/dL
Units mg/dL
Test Methodology Quantitative Spectrophotometry
Test Turnaround Time 1 Day
Limitations Sodium citrate, EDTA, and NaF potassium oxalate interfere
Shipping Requirements Refrigerated
Specimen Stability 7 Days RT
7 Days RF
Reject Criteria Gross Hemolysis, Gross Lipemia, Sodium citrate, EDTA, and NaF potassium oxalate interfere
Laboratory Developed Test (LDT) Yes
CMS Guidance None
References 1. Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company, 1999
2. Llach F, Felsenfeld AJ, Haussler MR. The pathophysiology of altered calcium metabolism in rhabdomyolysis-induced acute renal failure. Interactions of parathyroid hormone, 25-hydroxycholecalciferol, and 1,25-dihydroxycholecalciferol. N Engl J Med. 1981 Jul 16; 305(3):117-123.
3.Baldwin TE, Chernow B: Hypocalcemia in the ICU. J Crit Illness 1987;2:9-16
4. Strewler GJ, Nissenson RA. Hypercalcemia in malignancy. West J Med. 1990 Dec; 153(6):635-640 (review).