FTA-ABS

Definition

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

This test is used to confirm whether a positive screening test for syphilis means there is a true infection.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

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 used routinely to confirm whether a positive screening test for syphilis (either VDRL or RPR ) reflects true infection with syphilis. It may also be done when either primary or tertiary syphilis are suspected and the initial screening tests are negative, because screening tests during these stages of syphilis may be falsely negative.

Normal Values

A negative or non-reactive result indicates no current or past infection with syphilis.

What abnormal results mean

A positive FTA-ABS usually indicates infection with syphilis. This test will remain positive for life even if an individual has received appropriate treatment.

Other illnesses such as yaws and pinta may also result in positive FTA-ABS results.

What the risks are

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Special considerations

FTA-ABS will remain positive for life even if syphilis has been adequately treated. Therefore, it cannot be used to monitor the treatment of syphilis.

Illustrations

Blood test

Page Content:

Fluorescent treponemal antibody absorption test ; fluorescent treponemal antibody absorption test