FTA-ABS Blood Test

Written by Corinna Underwood | Published on June 15, 2012
Medically Reviewed by George Krucik, MD

FTA-ABS Blood Test

Your body’s immune system produces proteins known as antibodies when harmful substances are detected. These harmful substances, called antigens, take many forms, including parasites, viruses, fungi, and bacteria.

The FTA-ABS blood test (fluorescent treponemal antibody absorption test) is used to detect the presence of antibodies that react to the bacteria Treponema pallidum. These bacteria cause syphilis.

Syphilis is a sexually transmitted disease. It is spread by means of direct physical contact with syphilis sores, usually during sex. Sores can occur on the penis, vagina, anus or rectum.

What the Test Addresses

Your doctor may order this test to confirm a positive screening test for syphilis or if you have symptoms of syphilis, such as:

  • small round sores on the genitals or mouth
  • swollen lymph nodes
  • itchy rash on hands and feet

Your doctor may also order this test if you:

  • are being treated for another sexually transmitted disease
  • are pregnant (syphilis can kill a growing fetus if left untreated)
  • are about to get married (in some states)
  • have non-specific symptoms similar to those of syphilis
  • have had a negative syphilis test (to rule out the possibility of a false negative test)

How Is the Test Administered?

Your doctor will need to take a sample of blood from your arm. First the site will be cleaned with a swab of rubbing alcohol. The needle will then be inserted into a vein and a vial will be attached to fill with blood. When enough blood has been drawn, the needle is removed and the site is covered with a cotton pad and bandage.

The blood sample will then be sent to a laboratory for analysis.

Understanding the Results

Normal Results

A normal test result will give a negative reading for the presence of antibodies. This means that you are not currently infected with syphilis, and you have not been previously infected with this disease.

Abnormal Results

If your test result is positive, you have contracted a syphilis infection. Your test result will always be positive even if you have previously been diagnosed with syphilis and it has been successfully treated. For this reason, the FTA-ABS test cannot be used to monitor the effectiveness of syphilis treatments.

A false positive FTA-ABS test may be caused by another disease.

Yaws is a chronic infection of the bones, joints, and skin, caused by the same bacteria that cause syphilis. However, it is not a sexually transmitted disease. According to the National Institutes of Health (NIH), yaws mainly affects children in rural, tropical areas such as India, West Africa, and Latin America (NIH, 2012).

Pinta is a disease that affects the skin. It is caused by the bacteria Treponema carateum. According to Cambridge Histories Online, it is predominantly found in rural societies in Mexico and Central and South America (CHO, 1993).

A false positive may also occasionally occur in women with lupus. Lupus is an autoimmune disorder.

What Are the Risks of the Test?

As with any blood test, there are minimal risks of experiencing minor bruising at the needle site. In rare cases, the vein may become swollen after blood is drawn. This condition, known as phlebitis, can be treated with a warm compress several times each day.

Ongoing bleeding could be a problem if you suffer from a bleeding disorder or you are taking blood-thinning medication such as warfarin (Coumadin) or aspirin.

Preparation for the Test

There are no special preparations necessary for this test. You should inform your doctor if you are taking any blood-thinning medications such as warfarin (Coumadin). Your doctor may advise you to stop taking certain medications.

What to Expect After the Test

If you have tested positive for syphilis and it is in the early stages, it can be relatively easy to cure. Your doctor will treat you by injecting penicillin directly into the muscle. You will receive a follow-up blood test at three-month intervals for the first year and then one year later to ensure the treatment has been effective.

Unfortunately, if you are suffering from syphilis in its later stages, the damage to your organs and tissues is irreversible.

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