Test ID: FRT4
T4 (Thyroxine), Free, Serum
Method Description 
Describes how the test is performed and provides a method-specific reference
This is a chemiluminometric immunoassay. Free thyroxine (FT4) is measured using an automated, competitive, chemiluminescent immunoassay on the Advia: Centaur instrument. FT4 in the specimen competes with an acridinium ester-labeled analog of thyroxine (T4) for a limited amount of polyclonal rabbit anti-T4 antibody, which is covalently coupled to paramagnetic particles. An inverse relationship exists between the amount of FT4 in the patient specimen and the amount of relative light units detected by the system.(Package insert: Bayer Advia: Centaur. Bayer Diagnostics. East Walpole, MA)
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.
Same day/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
7 days
Performing Laboratory Location The location of the laboratory that performs the test
Rochester
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