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What is an Antinuclear Antibody (ANA) test?

Our immune system is our main line of defence against invading pathogens and foreign substances, such as viruses and bacteria; however, in autoimmune disorders, such as rheumatoid arthritis and systemic lupus erythematosus (SLE), it starts attacking healthy tissues. This response results in the production of antinuclear antibodies or ANAs, which leads to inflammation and pain in tissues and organs.

An ANA test is done to detect and measure the amount and pattern of these antibodies in the bloodstream. Since these antibodies specifically target the nucleus, they are termed as ANAs.

When done along with a physical examination and additional tests, ANA test can help identify various autoimmune disorders.

Alternate terms for this test include ANA, Fluorescent Antinuclear Antibody, FANA or ANA screen.

  1. Why is an ANA test performed?
  2. How do you prepare for an ANA test?
  3. How is an ANA test performed?
  4. What do ANA test results indicate?

An ANA test is done to diagnose the following conditions:

The common signs and symptoms of autoimmune disorders are:

  • Low-grade fever
  • Persistent fatigue
  • Tiredness and weakness
  • Unexplained weight loss
  • Pain in one or more joints (as in arthritis)
  • Skin rashes
  • Red rash (the shape of a butterfly across the nose and cheeks is seen in lupus)
  • Skin sensitivity to light
  • Hair loss
  • Muscle pain
  • Feeling of numbness or tingling in hands or feet
  • Inflammation and damage to various organs and tissues (kidneys, lungs, heart, central nervous system and blood vessels)

No special preparation is needed for this test. However, it is important to inform your doctor about any current medication or supplements, if you are on any. He/she can advise you to stop certain medications that can alter test results. Any long-term infection or viral infection can also affect test results, so make sure you inform your doctor about them, if any.

A blood sample will be collected by drawing blood from a vein in your arm. You may feel a momentary pricking pain when the needle goes in. After sample collection, a cotton ball or gauze pad will be placed over that area to stop bleeding. The sample is collected in a sterile vial or a test tube and sent to a laboratory for analysis.

There is a minimal risk of light-headedness and bruising at the site of injection. However, at most times, these symptoms disappear quickly. Rarely, an infection may occur at the site of withdrawal of blood. 

Results of an ANA test can vary depending upon the method used and the age, gender, and health history of the person. So, it is best that you talk to a physician to get the correct interpretation of results

A positive ANA test means that ANAs are present in the body. They are measured in titres. A titre above 1:160 gives a positive test result.

A positive result can be due to the following conditions:

  • Autoimmune connective tissue diseases:
    • Rheumatoid arthritis: A positive ANA test result can be seen in more than one-third of people with rheumatoid arthritis
    • SLE: Patients with SLE will have a positive ANA test result, but not all people who show a positive ANA will have SLE
    • Scleroderma: Approximately, 60-85% of people with this condition test positive for ANA.
    • Sjögren syndrome: Approximately, 80% of people with Sjögren syndrome show positive ANA test results
    • Juvenile idiopathic arthritis (arthritis in children)
    • Polymyositis
    • Raynaud's syndrome (a medical condition, in which, spasms in arteries cause episodes of reduced blood flow)
  • Autoimmune diseases:
  • Antihypertensive medicines
  • Anti-tuberculosis drugs
  • Medicines for heart disease
  • Viral infections
  • Short-term infections

A negative result suggests the absence of an autoimmune disorder. However, since autoimmune diseases manifest in an episodic manner, the test should be performed again if symptoms recur. Furthermore, a negative result may appear if the autoimmune condition is in the remission phase.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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References

  1. Petri M, Orbai A-M, Alarcón GS, Gordon C, Merrill JT, Fortin PR, et al. Derivation and validation of the Systemic Lupus International Collaborating Clinics classification criteria for systemic lupus erythematosus.. Arthritis Rheum. 2012 Aug;64(8):2677-86. PMID: 22553077
  2. UW Health. Antinuclear Antibodies (ANA). University of Wisconsin Hospitals; Wisconsin, United States. [internet].
  3. Health Link. Antinuclear Antibodies (ANA). British Columbia. [internet].
  4. University of Rochester Medical Center. Antinuclear Antibody. Rochester, New York. [internet].
  5. MedlinePlus Medical Encyclopedia: US National Library of Medicine; ANA (Antinuclear Antibody) Test