Anti -TPO Test: Introduction, Test Result, Unit, Normal Range, Assaying Method, and Keynotes

Introduction

Anti -TPO test is an autoantibody assay that is against thyroperoxidase (TPO) (antigen). TPO is an enzyme present in thyroid hormone formation, catalyzing the oxidation of iodide on tyrosine residues in thyroglobulin for the synthesis of triiodothyronine (T3) and thyroxine (tetraiodothyronine -T4). This enzyme is a membrane-associated hemo-glycoprotein. It expresses only in thyrocytes and is one of the most important thyroid gland antigens. Disorders of the thyroid gland are common due to autoimmune mechanisms with the production of autoantibodies. Anti-TPO antibodies cause thyroid dysfunction and the pathogenesis of hypothyroidism by activating complement. This anti -TPO test is clinically significant in autoimmune thyroid diseases like Hashimoto’s thyroiditis ((inflammation of the thyroid gland that reduces thyroid production), idiopathic myxedema (severely low production of thyroid hormones), and Graves disease (excess production of thyroid hormones). Its highest level appears in Hashimoto thyroiditis/disease.

Anti- TPO Test-Test Result, Unit, Normal Range, and Assaying Method

Keynotes

• ECLIA stands for electrochemiluminescence immunoassay.
• An anti-TPO test is ordered by clinicians (especially clinical endocrinologists) to diagnose autoimmune disorders of the thyroid such as Hashimoto’s thyroiditis, Graves disease, and idiopathic myxedema. It also assists distinguish between autoimmune thyroid and non-autoimmune thyroid diseases like Goiter (enlarged thyroid gland).
• The prevalence of TPO antibodies is about 90% of Hashimoto’s disease.
• It is also found in the course of Graves disease (60%-80%).
• The presence of this autoantibody is associated with an increased risk of developing overt hypothyroidism in patients with subclinical hypothyroidism and thus endocrinologists use this assay as a diagnostic tool in deciding to treat a patient with subclinical hypothyroidism.
• Anti-TPO tests may be positive (10% – 12% cases) in a healthy population with normal thyroid function.
• No fasting and special preparation are required for this test. Blood is drawn in a clot activator tube for this assay similar to routine biochemical tests like blood sugar, and creatinine.

Further Readings

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7505314/
• https://www.mayocliniclabs.com/api/sitecore/Test
• https://www.hindawi.com/journals/ad/2019/1684074/
• https://www.ilexmedical.com/files/PDF/Anti-TPO_ARC.pdf
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478324/