Calcium, Plasma

Diagnostic Use

Calcium is a plasma electrolyte which plays an important role in many physiological processes throughout the body. Measurement of total calcium includes both the unbound and bound fractions of calcium in the blood.

Plasma calcium may be requested in patients with symptoms of, or those at risk of, a disorder of calcium homeostasis.

Department

Core Biochemistry

Delphic Registration Code

CA

Constituent Tests

• Calcium (corrected), Plasma

Synonyms

Ca

Turnaround Time

3 hours

Test Code

3521

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin - Non-gel (Green Cap)

Acceptable

• Serum (Red Cap)
• SST II (Gold Cap)
• Lithium Heparin - Gel (Green Cap)

Preferred Sample Volume (ml)

4.5

No of Samples Required

1

Interferences

Contamination with tube additives such as EDTA, oxalate and citrate will cause spuriously low calcium results. Calcium should only be measured on serum tubes or (balanced) lithium heparin tubes.

Additional Specimen Information

Paediatric Specimen - Heparin microtainer tube 600 µL

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

0.1

Transport to Lab

Chilled (2 - 8 degrees Celsius)
If overnight - Chilled (2 - 8 degrees Celsius)

Interpretation

Calcium results must be interpreted in the clinical context.  Total calcium is usually reported with a corrected calcium, which more accurately reflects plasma calcium status if the albumin concentration is abnormal.  Nonetheless, the best test of calcium status is ionised calcium, collected anaerobically in a blood gas syringe.

Hypercalcaemia and hypocalcaemia both have many different underlying causes. Measurement of PTH with calcium may assist in narrowing down the differential diagnosis.

Common causes of hypercalcaemia include dehydration, hyperparathyroidism and malignancy.

Common causes of hypocalcaemia include hypoparathyroidism, renal failure and hypokalaemia.

Reference Intervals

Age	Reference Interval (mmol/L)
0d to <1w	1.9 – 2.8
1w to <26 w	2.2 – 2.8
26w to <18y	2.2 – 2.7
18y to Adult	2.2 – 2.6

Test Method

Photometric colour test for the quantitative determination of total calcium performed on Beckman Coulter AU5822 analyser using Beckman Coulter reagents

Non-Funded Test Cost

$3.24 (Exclusive of GST)

Billing Code

3521

Contact Information

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