TSI (Thyroid Stimulating Immunoglobulin) Test
This test measures thyroid stimulating immunoglobulins, or TSI, in a blood sample. TSI is a group of IgG immunoglobulins associated with Graves' disease, a well-known form of hyperthyroid disease.
About this test
TSI is measured using an in vitro bioassay on a serum sample. Because Graves' disease is caused by these immunoglobulins, a TSI result is one piece of information a clinician may use alongside other thyroid findings when Graves' disease is part of the clinical picture.
Quest describes TSI as potentially useful in predicting whether antithyroid drug therapy is likely to be effective, since markedly elevated TSI levels are associated with a lower likelihood of response. TSI may also assist in predicting hyperthyroidism in neonates, since these immunoglobulins can cross the placenta from a mother with hyperthyroidism to her baby, which is why a clinician may track TSI during pregnancy in that context.
Test details
| Collection | Quest patient service center |
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Quest resources
Additional details
What this test looks at
The test reports one value: the level of thyroid stimulating immunoglobulins in serum, measured by in vitro bioassay. It is a different product from TRAb, which measures antibody activity by a separate binding-based method, so a clinician chooses between the two based on which type of antibody information is needed for the situation.
This test isn't part of the Celio Health store at the moment, so it can't be ordered or requested here. The test menu lists everything that can.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does this test measure?
It measures thyroid stimulating immunoglobulins (TSI) in a serum sample, using an in vitro bioassay.
How is the sample collected?
The test uses a serum sample from a routine blood draw.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
What is TSI used for?
Quest describes TSI as associated with Graves' disease and as potentially useful in predicting response to antithyroid drug therapy and in predicting hyperthyroidism in neonates.
Is TSI the same as TRAb?
No. Both relate to antibodies affecting the TSH receptor, but TSI and TRAb are separate Quest products measured by different methods.