Test ID: T4TF
T4 (Thyroxine), Total and Free
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
8684
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Yes
Useful For Suggests clinical disorders or settings where the test may be helpful
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| T4 | T4 (Thyroxine), Total Only, S | Yes | Yes |
| FRT4 | T4 (Thyroxine), Free, S | Yes | Yes |
Method Name A short description of the method used to perform the test
FRT4/8725: Chemiluminometric Immunoassay
T4/8724: Immunoenzymatic Assay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
T4 (Thyroxine), Total and Free
Specimen Type Describes the specimen type needed for testing
Serum
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:
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 1 mL
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.
0.6 mL
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
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 | Refrigerated (preferred) | 7 days |
| Frozen | 60 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
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.
T4 (THYROXINE), TOTAL ONLY
> or =12 months: 5.0-12.5 mcg/dL
Reference values have not been established for patients that are <12 months of age.
T4 (THYROXINE), FREE
0.8-1.8 ng/dL
Elevated values are seen in patients on thyroxine therapy.
Interpretation Provides information to assist in interpretation of the test results
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
Method Description Describes how the test is performed and provides a method-specific reference
See individual test descriptions for:
-T4/8724 T4 (Thyroxine), Total Only, Serum
-FRT4/8725 T4 (Thyroxine), Free, Serum
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; 6 a.m.-3 p.m.
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.
1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
2 days
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
See Individual Unit Codes
Performing Laboratory Location The location of the laboratory that performs the test
Rochester
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.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
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.
84436-Total
84439-Free
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 |
|---|---|---|
| FRT4 | T4 (Thyroxine), Free, S | 3024-7 |
| T4 | T4 (Thyroxine), Total Only, S | 3026-2 |
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