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HelpMayo Test ID CAI Calcium, Ionized, Serum
Specimen Required
Container/Tube: Serum gel or serum gel microtainer
Specimen Volume: Full tube
Collection Instructions:
1. Allow blood to clot for 30 minutes.
2. Serum gel tube/microtainer must be centrifuged within 1 hour of collection. Centrifuge with stopper in place for 7 minutes at 3000 rpm to ensure that the gel barrier separates the serum and cells.
3. Keep specimen anaerobic; do not aliquot.
Useful For
Assessing calcium states during liver transplantation surgery, cardiopulmonary bypass, or any procedure requiring rapid transfusion of whole blood in neonates and critically ill patients
Second-order test in the evaluation of patients with abnormal calcium values
Method Name
Ion-Selective Electrode (ISE)
Reporting Name
Calcium, Ionized, SSpecimen Type
Serum SSTSpecimen Minimum Volume
1.75 mL in a 3.5 mL (50% full) in serum gel tube or 1 full serum gel microtainer
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum SST | Refrigerated | 7 days | SERUM GEL TUBE |
Reject Due To
| Gross hemolysis | Reject |
| Tubes less than 50% full Specimens that have been aliquoted, opened, or poorly centrifuged |
Reject |
Clinical Information
Ionized calcium, which accounts for 50% to 55% of total calcium, is the physiologically active form of calcium.
Low ionized calcium values are often seen in kidney disease, critically ill patients, or patients receiving rapid transfusion of citrated whole blood or blood products.
Increased serum ionized calcium concentrations may be seen with primary hyperparathyroidism, ectopic parathyroid hormone-producing tumors, excess intake of vitamin D, or various malignancies.
Nomograms have been used to calculate ionized calcium from total calcium, albumin, and pH values. However, calculated ionized calcium results have proven to be unsatisfactory. A Mayo study of 114 patients found significant differences between ionized and total calcium in 26% of patients.
Reference Values
IONIZED CALCIUM
≤13 days old: Not established
14 days-<1 year: 5.21-5.99 mg/dL
1-<2 years: 5.04-5.84 mg/dL
2-<3 years: 4.87-5.67 mg/dL
3-23 years: 4.83-5.52 mg/dL
24-97 years: 4.57-5.43 mg/dL
≥98 years: Not established
pH
≤13 days old: Not established
14 days-97 years old: 7.35-7.48
≥98 years old: Not established
For SI unit Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Interpretation
Serum ionized calcium concentrations 50% below normal will result in severely reduced cardiac stroke work. With moderate to severe hypocalcemia, left ventricular function may be profoundly depressed.
Ionized calcium values are higher in children and young adults.
Ionized calcium result has been adjusted to pH 7.40 to account for changes in specimen pH that may occur during transport. Ionized calcium concentration increases approximately 0.2 mg/dL per 0.1 pH unit decrease.
Cautions
Proper specimen handling is necessary to ensure accurate results.
Clinical Reference
Rifai N, Horwath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018
Method Description
The pH and ionized calcium sensors in the GEM Premier 3500 Analyzer are based on the principle of ion-selective electrodes; that is, an electrical potential can be established across a membrane that is selectively permeable to a specific ion.(Instruction manual: GEM Premier 3500 Analyzer Operator's Guide. Instrumentation Laboratory; 03/2015)
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 daySpecimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82330
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CAI | Calcium, Ionized, S | 57333-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CAIS | Calcium, Ionized, S | 57333-7 |
| PHCC | pH | 2753-2 |