Thyroid peroxidase test is a test that measures the level of an antibody that is directed against thyroid peroxidase (TPO).

Autoantibodies to thyroid peroxidase (TPOAb) are produced within the body. The presence of TPOAb in the blood reflects a prior attack on the thyroid tissue by the body's immune system.

What does a positive thyroid peroxidase test mean?

Most people with chronic Hashimoto’s thyroiditis display a positive TPO test. The test is also positive in lesser numbers of people with other thyroid diseases.

Other autoimmune disorders that may cause a positive TPOAb test include:

Sjogren's syndrome,

lupus,

rheumatoid arthritis

pernicious anemia

About 3% of people with a positive TPOAb test show no evidence of disease.

The chance of having a positive TPOAb test is greater in females and increases with age.

The test is used first to determine if someone has an autoimmune disease. If the results are positive, then it is run frequently to determine if the theropy being used to manage the antibodies is working properly.

This test goes by a confusing number of names, including:

thyroid peroxidase (TPO) antibody (TPOAb) test,

thyroid peroxidase autoantibody test,

antimicrosomal antibody test, and

antithyroid microsomal antibody test.