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FTA-ABS blood test

Fluorescent treponemal antibody absorption test

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Definition

The FTA-ABS test is used to detect antibodies to the bacteria Treponema pallidum, which causes syphilis.

How the Test is Performed

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

How to Prepare for the Test

No special preparation is necessary.

Normal Results

A negative or nonreactive result means that you do not have a current or past infection with syphilis.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.

Risks

Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

What Abnormal Results Mean

A positive FTA-ABS is often a sign of a syphilis infection. This test result will remain positive for life even if syphilis has been adequately treated. Therefore, it cannot be used to monitor the treatment of syphilis or determine that you have active syphilis.

Other illnesses, such as yaws and pinta (two other kinds of skin diseases), may also result in positive FTA-ABS results. Sometimes, there can be a false-positive result, most often in women with lupus.

Why the Test is Performed

This test is done routinely to confirm whether a positive screening test for syphilis (either VDRL or RPR) means you have a current syphilis infection.

It may also be done when other syphilis tests are negative, to rule out a possible false-negative result.

Review Date: 9/27/2017
Reviewed By: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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