Antimicrosomal Antibody Test

Test Description
Microsomes are lipoproteins that are normally present within the epithelial cells of
the thyroid. In some types of thyroid disorders, these microsomes escape from their
normal locations. Once liberated, these substances appear as antigens to the body.
In response, the body produces antibodies against the microsomes, leading to
inflammation and destruction of the thyroid gland. Antimicrosomal antibodies are
present in the majority of patients diagnosed with Hashimoto’s thyroiditis. The most
dilute serum in which antimicrosomal antibodies are detected is called the titer. This
test is usually performed in conjunction with the antithyroglobulin antibody test

Normal Values

      Titer < 1:100

Possible Meanings of Abnormal Values

Increased
Autoimmune hemolytic anemias
Granulomatous thyroiditis
Hashimoto’s thyroiditis
Juvenile lymphocytic thyroiditis
Myasthenia gravis
Myxedema
Nontoxic nodular goiter
Pernicious anemia
Primary hypothyroidism
Rheumatoid arthritis
Sjögren’s syndrome
Systemic lupus erythematosus
Thyroid cancer

Contributing Factors to Abnormal Values

• Drugs that may increase antimicrosomal antibody titers: oral contraceptives.

Interventions/Implications

Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
  Procedure
• A 7-mL blood sample is drawn in a red-top collection tube.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued
   bleeding.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.

Clinical Alerts                     
• This test is usually performed in conjunction with the antithyroglobulin antibody
test.