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Test ID: Calcium
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Calcium
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Useful For
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Screening, diagnosis, and monitoring of medical conditions related to bones, heart, thyroid, nerves, kidney and gastrointestinal tract.
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Method name and description
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Calcium ions react with 5‑nitro‑5’‑methyl‑BAPTA (NM‑BAPTA) under alkaline conditions to form a complex. This complex reacts in the second step with EDTA.
alkaline pH
Ca2+ + NM‑BAPTA  calcium‑NM‑BAPTA complex
calcium‑NM‑BAPTA complex + EDTA NM‑BAPTA + calcium EDTA complex
The change in absorbance is directly proportional to the calcium concentration and is measured photometrically.
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Clinical information
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Calcium is the most abundant mineral element in the body with about 99% in the bones primarily as hydroxyapartite. The remaining calcium is distributed between the various tissues and extracellular fluids where it performs a vital role for many life sustaining processes, amomg which are: involvement in blood coagulation, neuromuscular conduction, excitability of skeletal and cardiac muscle, enzyme activation, and the preservation of cell membrane integrity and permeability
Serum calcium levels are controlled by PTH, calcitonin, and Vitamin D. An imbalance in any of these modulators leads to alterations of the body and serum calcium levels. Increased serum PTH or Vitamin D are usually associated with hypercalcemia. Increased levels may also be observed in multiple myeloma, and other neoplastic diseases. Hypocalcemia maybe observed in hypoparathyroidism, nephrosis, and pancreatitis.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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Fresh serum collected in the fasting state is the preferred specimen.
Sera from patients receiving EDTA (treatment of hypercalcemia) are unsuitable for analysis.
Serum or plasma should be separated from blood cells as soon as possible.
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Storage and transport instructions
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Storage: 7 days at 15 – 25°C
3 weeks at 2 – 8°C;
8 months at ‑20 °C (± 5 °C)
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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Sex
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Age
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Reference Interval (mmol/L)
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Male /Female
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From
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To
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From
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To
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Male /Female
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0 days
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28 days
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2.0
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2.7
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Male /Female
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28 days
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16 years
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2.2
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2.7
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Male /Female
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16 years
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150 years
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2.2
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2.6
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(This is an estimate of calcium concentration assuming normal albumin concentration is 44.1 g/l.)
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Factors affecting test performance and result interpretation
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The interference of intravenously administered gadolinium containing MRI (magnetic resonance imaging) contrast media (Omniscan®) at higher concentrations were observed.
Physiological plasma concentration of Sulfasalazine or Sulfapyridine may lead to false results.
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
STAT: 1 hour
Routine: One working day
Specimen retention: 4 days
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