New Blood Test for Graves' Disease
FDA Approved Lab Assay for Thyroid Stimulating Immunoglobulins (TSI)
Sep 7, 2009
Diagnostic HYBRIDS, a research and development company in Athens, Ohio, received FDA clearance for the Thyretain™ TSI Reporter Bioassay. The Thyretain assay is the first FDA-cleared blood testing method that specifically detects thyroid stimulating immunoglobulins (TSI, also known as stimulating TSH receptor antibodies). Other assays in use for TSI have not been FDA approved and may lack the sensitivity and specificity of the new Thyretain assay.
TSI and Graves’ Disease
Graves’ disease is an autoimmune thyroid disorder that causes hyperthyroidism. Graves’ disease is the primary cause of hyperthyroidism in patients younger than 45 years. The second leading cause of hyperthyroidism is toxic multinodular goiter (TMG). Graves’ disease affects 1-2 percent of the population and is most prevalent in women in their forties. Eighty percent of Graves’ disease cases occur in women.
Graves’ disease is directly caused by TSI. TSI antibodies act in place of the pituitary hormone thyroid stimulating hormone (TSH). In doing so, TSI latch on to the receptors of thyroid cells and order the cells to produce excess thyroid hormone. TSI also contribute to other manifestations in Graves' disease, such as thyroid eye disease and pretibial myxedema.
Graves’ disease, which is considered a self-limiting disorder, can be difficult to diagnose because early on symptoms typically wax and wane. Periods in which symptoms occur typically alternate with periods of remission. Symptoms can also be vague, such as headache and nervousness and the predominant symptoms of an individual can change over time.
TSI and Hashitoxicosis
The Thyretain Assay is also an important tool for diagnosing TSI in patients with Hashitoxicosis. In Hashitoxicosis, patients primarily have Hashimoto’s thyroiditis but also have TSI. TSI cause spikes in thyroid hormone and transient flares of hyperthyroidism.
TSI and Euthyroid Graves’ Disease
The Thyretain Assay is also important for helping to diagnose euthyroid Graves’ disease. In this condition individuals show symptoms of thyroid eye disease although they have normal thyroid function. However, these individuals typically have high concentrations of both TSI and blocking TSH receptor antibodies. In this case, the blocking antibodies prevent TSI from causing hyperthyroidism, and both types of antibodies contribute to the autoimmune eye condition called Graves’ ophthalmopathy. Consequently, patients have normal thyroid function tests (TSH, FT4, FT3) with symptoms of Graves' ophthalmopathy.
Thyretain Blood Assay
The Thyretain blood assay can help with early diagnosis and better patient management. Using this assay, TSI can be detected in the blood before overt or serious conditions of hyperthyroidism occur.
The Thyretain assay uses standard laboratory equipment, making it available to even small laboratories. The Thyretain assay is not affected by the protein interferences, including other antibodies, that are seen in other methods and immunoassays.
Benefits
When used to test patients suspected of hyperthyroidism or who have a strong family history early in the course of their disease, the Thyretain leads to an earlier diagnosis and treatment. Earlier diagnosis of Graves’ disease can lead to an increased awareness and consideration of medical therapy, eliminating the trend of rushing patients into having radioiodine ablation.
Expected Thyretain Test Release
The Thyretain TSI Reporter BioAssay will be made available through major commercial reference laboratories in the United States and in select hospital systems around the end of September. More information can be obtained through Diagnostic HYBRIDS.
Resource:
Diagnostic HYBRIDS Releases Thyretain™ for the Specific Detection of Thyroid Stimulating Immunoglobulin (TSI), Press Release, August 24, 2009
 |
