The FTA-ABS test is a blood test to detect antibodies to the bacteria Treponema pallidum, which causes syphilis.
This test is used when a screening test for syphilis is positive to confirm that there is a true infection.
Fluorescent treponemal antibody absorption test
How the Test is Performed
A blood sample is needed. For information on how this is done, see: Venipuncture
How to Prepare for the Test
No special preparation is necessary.
How the Test will Feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
This test is done routinely to confirm whether a positive screening test for syphilis (either VDRL
) 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.
A negative or nonreactive result means there 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 doctor about the meaning of your specific test results.
What Abnormal Results Mean
A positive FTA-ABS is usually 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 may also result in positive FTA-ABS results. Occasionally there can be a false positive result, most often in women with lupus.
Veins and arteries vary in size from one patient 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 light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Tramont EC. Treponema pallidum (syphilis). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2009:chap 238.
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, Bethanne Black, and the A.D.A.M. Editorial team.