Calcium (corrected), Plasma

Diagnostic Use

Calcium is a plasma electrolyte which plays an important role in many physiological processes throughout the body.

Approximately 50% of the plasma calcium pool is bound to albumin, with 10% bound to other anions, and 40% unbound and biologically available. As such, the total calcium is greatly influenced by the plasma albumin concentration. The corrected calcium (more correctly referred to as albumin-adjusted calcium) is a calculated parameter that gives information as to what the total calcium is likely to be assuming that the albumin level was restored to the middle of the reference interval.

Corrected calcium will be higher than the total calcium in hypoalbuminaemia, and will be lower than total calcium in hyperalbuminaemia.

Department

Core Biochemistry

Delphic Registration Code

COCA

Constituent Tests

• Albumin, Plasma

Synonyms

Albumin Corrected Calcium
Corrected Calcium

Turnaround Time

3 hours

Test Code

5772

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. Plasma 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

Corrected calcium results must be interpreted in the clinical context.  Although the corrected calcium is more accurate than the total calcium if the plasma albumin is abnormal, the best test to assess calcium status is ionised calcium on a blood gas specimen.

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

Adults: 2.2 – 2.6 mmol/L

 

Test Method

Calculated parameter:
Corrected Calcium = Calcium + 0.012*(39.9 - Albumin)

Contact Canterbury Health Laboratories on +64 3 364 0484 or email LabInfo@cdhb.health.nz

Contact Information

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