Test ID: IONCG
Calcium, Ionized, Serum
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Assessing calcium states during liver transplantation surgery, cardiopulmonary bypass, or any procedure requiring rapid transfusion of whole blood in neonates and in critically ill patients
Second order test in the evaluation of patients with abnormal calcium values
Method Name A short description of the method used to perform the test
Ion-Selective Electrode (ISE)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Calcium Ionized, Serum
Free Calcium
Ionized Calcium, Serum
Ca (Calcium)
Calcium (Ca)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Serum gel
Specimen Volume: Full tube
Collection Instructions:
1. Allow blood to clot for 30 minutes.
2. Centrifuge with stopper in place for 10 minutes at 2,000 rpm to ensure that the gel barrier separates the serum and cells.
3. Keep specimen anaerobic (do not transfer).
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross OK |
| Icterus | NA |
| Other | Specimen in plastic vial |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum SST | Refrigerated | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 renal 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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Males
<1 year: not established
1-19 years: 4.90-5.50 mg/dL
> or =20 years: 4.65-5.30 mg/dL
Females
<1 year: not established
1-17 years: 4.90-5.50 mg/dL
> or =18 years: 4.65-5.30 mg/dL
Interpretation Provides information to assist in interpretation of the test results
Serum ionized calcium concentrations 50% below normal 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 values vary inversely with pH, approximately 0.2 mg/dL per 0.1 pH unit change.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Proper specimen handling is necessary to ensure accurate results.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Toffaletti JG: A clinical review of ionized calcium: a better indicator than total calcium. Waltham, MA, Nova Biomedical, 1998
2. Tietz: Textbook of Clinical Chemistry and Molecular Diagnostics, Fourth Edition, 2006. Measurement of free (ionized) Calcium; Effect of PH & Anticoagulant.
Method Description Describes how the test is performed and provides a method-specific reference
Ionized calcium is measured using an ion-selective electrode on NOVA Stat Profile Critical Care Xpress (CCX). The sensor requires a sensing (ion-selective) membrane, a reference electrode, and an internal filling solution. Internal filling solution provides a fixed concentration of the ion and the sample provides a second ion concentration. A suitable electrode membrane is selectively permeable to the ionized calcium in the sample. This selective permeability establishes an electrical potential as the charge associated with the ion leaves its counter-ion behind in solution. The magnitude of this electrical potential is determined by the concentration difference between the two sides of the membrane.
pH is measured using a hydrogen ion-selective glass membrane. One side of the glass is in contact with a solution of constant pH. The other side is in contact with a solution of unknown pH. A change in potential develops, which is proportional to the pH difference of these solutions. This change in potential is measured against a reference electrode of constant potential. The magnitude of the potential difference is a measure of the pH of the unknown solution.
Ionized calcium and pH are measured concurrently and the ionized calcium value is calculated at a standard pH of 7.40. (Instructional Manual: NOVA Stat Profile Critical Care Xpress [CCX] Nova Biomedical, Waltham, MA, November 2007)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday, Sunday; Available STAT
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
82330
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 11304 | Calcium, Ionized, S | 17863-2 |
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