Thyroid-Stimulating Immunoglobulin (TSI), Serum
Method Description Describes how the test is performed and provides a method-specific reference
This bioassay compares the cyclic adenosine monophosphate (cAMP) production of thyroid-stimulating hormone (TSH)-responsive cells upon exposure to patient serum with that obtained in the same cells after exposure to normal control serum.
The assay uses Chinese hamster ovary cells that have been permanently transfected with the human thyroid-stimulating hormone receptor (TSHR) and a luciferase expression construct under the control of a cAMP responsive promoter. Luciferase transcription in these cells is proportional to the concentration of intracellular cAMP.
The cells are grown to near-confluence. An aliquot of cells is then incubated with each diluted patient serum. Cells are lysed at the end of incubation, luciferase substrate is added and chemiluminesence is measured in a luminometer. The ratio of the light-units produced in the cell-lysate exposed to patient serum divided by a control cell-lysate light-signal is the TSI index. (Preissner CM, Wolhuter PJ, Sistrunk JW, et al: Comparison of thyrotropin-receptor antibodies measured by four commercially available methods with a bioassay that uses Fisher-rat thyroid cells. Clin Chem 2003;49:1402-1404; Package insert: Thyroid Stimulating Immunoglobulin Assay. Diagnostic Hybrids)
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; 10 a.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.
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