Calcium, Ionized, Serum

Alternate Name: Calcium_Ionized_LC

  | Calcium Filterable; Calcium Unbound; IonCa

SAL Code:

421

CPT:

82330

Loinc:

17864-0

Turn Around Time:

2 days

Setup:

Daily

Units:

mg/dL

Department:

Chemistry

Methodology:

Ion-Selective Electrode

Specimen Requirements:

Primary Tube:

SST

Primary Substance:

Serum

Alternate Sample Info:

SEPARATE UNOPENED SST!

Temperature

Period

Stable Ambient:

14 Days

Stable Fridge:

14 days

Rejection Criteria:

Hemolysis; opened gel-barrier tube; gel-barrier not completely sealing the clot; plasma specimen; gross lipemia

Clinical Info:

Evaluate nonbound calcium, calcium metabolism, physiologically active calcium fraction, hyperparathyroidism, ectopic hyperparathyroidism. Occasionally useful when hypercalcemia coexists with abnormal protein state such as myeloma. Useful in assessing active calcium fraction in hypoproteinemia and acidosis when calcium is low.

Additional Information:

Calcium in serum exists ionized, bound to organic anions such as phosphate and citrate, and bound to proteins (mainly albumin). Of these, ionized calcium is the physiologically important form. Measurement of serum ionized calcium provides insight into the effect of total protein and albumin on serum calcium levels. A patient can have high total calcium, with normal ionized calcium and increased total protein and/or albumin, as in dehydration or in myeloma. Women have greater circadian variation of ionized calcium and intact PTH than men. There is an inverse relationship between ionized calcium and phosphate concentration.

Sample Collection:

Collect patient samples using standard phlebotomy techniques. Click here for additional collection instructions.

Test Limitations:

Total calcium (SAL# 308) remains the first line test for evaluation of calcium abnormality.

Specimen Handling Instructions:

Centrifuge and send unopened gel-barrier tube with vacuum intact and DO NOT FREEZE. It is critical that the vacuum not be disrupted. Exposure of the serum to room air causes a loss of carbon dioxide to the atmosphere. This changes the sample pH and can prevent the lab from measuring the ionized calcium. To ensure that testing can be performed, send a separate tube for ionized calcium and adhere a piece of labeling tape over the top of the tube with the following written on it “Ionized Calcium - DO NOT OPEN.”

Test Information:

Components: