Anti Thyroperoxidase Antibody (Anti-TPO) Test

The Anti-Thyroperoxidase Antibody (Anti-TPO) test measures the level of antibodies against thyroid peroxidase (TPO) in the blood. The test is also known as the anti-thyroid peroxidase antibody test, anti-thyroid microsomal antibody test, thyroid antimicrosomal antibody test, and TPOAb test. 

The thyroid gland is a small gland situated in front of the neck that produces thyroid hormones. These hormones have various important functions in the body, such as assisting in growth and development, controlling body temperature, and metabolism. In children, they help in the overall development and function of the brain.

Normally, the immune system produces antibodies to protect the body from infections. However, in autoimmune conditions, it mistakenly attacks healthy tissues. Thyroid peroxidase (TPO) is a protein in the thyroid gland that helps produce thyroid hormones. In certain autoimmune conditions, the immune system produces anti-thyroid peroxidase (anti-TPO) antibodies against this protein, which may interfere with normal thyroid function. The Anti-TPO test measures these antibodies in the blood and helps doctors diagnose autoimmune thyroid conditions such as Hashimoto’s disease and Graves’ disease. Early testing may help identify thyroid disorders before complications develop.

The antithyroid antibodies test is advised if you are experiencing the following symptoms of thyroid dysfunction:

• Feeling tired 
• Abnormal weight gain 
• Constipation 
• Increased sensitivity to cold 
• Muscle pain 
• Depression 
• Difficulty exercising 
• Slower increase in height in children 

It is also highly recommended for the following categories of people: 

• Pregnant women – Some pregnant women are advised to take the test to determine the risk of autoimmune thyroid disease, especially if they have thyroid symptoms or a history of infertility or recurrent pregnancy loss. 
• Individuals with a family history of thyroid disorders – People with a family history of Graves’ disease or Hashimoto’s disease are at a higher risk of developing these autoimmune disorders.
• Individuals with other autoimmune disorders – You are more likely to develop autoimmune thyroid disorders if you already have conditions like celiac disease (an autoimmune disorder affecting the small intestine), lupus (a chronic autoimmune condition that may affect many organs and body systems, including the skin, joints, and kidneys), type 1 diabetes, and rheumatoid arthritis (inflammation of the joints).

The recommended frequency of the Anti-TPO test varies depending on an individual’s health status, risk factors, and existing medical conditions. The table below outlines general guidelines for how often testing should be performed in different scenarios. 

The Anti-TPO test can help in the diagnosis of conditions, such as: 

• Graves’ disease – An autoimmune disorder that causes hyperthyroidism, or an overactive thyroid gland, which can result in complications affecting the heart. 
• Goitre – It refers to a condition with an enlarged thyroid and can be associated with a normally functioning thyroid gland, hypothyroidism, or hyperthyroidism. 
• Hashimoto’s disease – An autoimmune disorder that causes hypothyroidism (underactive thyroid). 
• Postpartum thyroiditis – An autoimmune inflammatory condition of the thyroid gland that occurs within one year after delivery in women whose thyroid gland was previously functional. 

Positive anti-TPO antibody results may also be seen in other conditions, such as subclinical hypothyroidism (an early form of hypothyroidism), subacute thyroiditis (a temporary inflammatory condition of the thyroid gland), systemic lupus erythematosus (a chronic autoimmune condition that may affect many organs and body systems, including the skin, joints, and kidneys), and rheumatoid arthritis. However, the Anti-TPO test is not primarily used to diagnose these disorders.

What to Expect Before the Anti-TPO Test

No fasting is required for a standalone Anti-TPO test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise Anti-TPO levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the Anti-TPO Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

In the Anti-TPO test, the primary parameter measured is: 

• The level of antibodies against the thyroid peroxidase enzyme.

The Anti-TPO test normal range is indicated in the table below. 

Note: The normal range may vary slightly depending on the laboratory and individual health conditions.

The table below provides a general interpretation of Anti-TPO test results based on whether levels are high or low.

Note: 

• High levels of these antibodies have also been linked with an increased risk of miscarriage, preeclampsia (associated with high blood pressure and protein in the urine after the 20th week of pregnancy), or premature birth. 
• Results should always be interpreted along with symptoms and other diagnostic test results. 

Like any other medical test, this test also has some risks and limitations. 

Risks:

•  The Anti-TPO test is generally safe and involves minimal risk. You may experience mild pain or slight bruising, which will resolve quickly on its own. 

Limitations: 

• Antithyroid antibodies may be detected if you have other autoimmune conditions, such as autoimmune haemolytic anaemia (a condition in which the immune system destroys red blood cells), autoimmune hepatitis (inflammation of the liver), rheumatoid arthritis (inflammation of joints), and Sjogren syndrome (an autoimmune condition affecting the tear and salivary glands). 
• An anti-TPO test provides only a single-point measurement and may not be enough to confirm a diagnosis on its own. 

Depending on your symptoms and results, your doctor may recommend additional tests to better understand your condition. These include: 

• TSH (thyroid-stimulating hormone) test
• Free T4 test
• Total T3 test
• Thyroid-stimulating immunoglobulin (TSI) and thyrotropin receptor antibody (TRAb) tests
• Thyroglobulin antibody (TgAb) test
• Radioactive iodine uptake test 
• Thyroid scan

Pro Tip: For the most stress-free experience, book an Anti-TPO on PharmEasy. Enjoy professional service and accurate results without stepping out of your house.