The fluorescent treponemal antibody absorption (FTA-ABS) test is a blood test that checks for the presence of antibodies to Treponema pallidum bacteria. These bacteria cause syphilis.
Syphilis is a sexually transmitted infection (STI) that’s spread through direct contact with syphilitic sores. Sores are most often present on the penis, vagina, or rectum. These sores aren’t always noticeable. You may not even know that you’re infected.
The FTA-ABS test doesn’t actually check for the syphilis infection itself. However, it can determine whether you have antibodies to the bacteria that cause it.
Antibodies are special proteins produced by the immune system when harmful substances are detected. These harmful substances, known as antigens, include viruses, fungi, and bacteria. This means that people who are infected with syphilis will have the corresponding antibodies.
The FTA-ABS test is often performed after other tests that screen for syphilis, such as the rapid plasma regain (RPR) and venereal disease research laboratory (VDRL) tests.
It’s usually done if these initial screening tests come back positive for syphilis. The FTA-ABS test can help confirm whether the results of these tests are accurate.
Your doctor may also order this test if you have symptoms of syphilis, such as:
- small, roundish sores on the genitals, which are called chancres
- a fever
- hair loss
- aching joints
- swollen lymph nodes
- an itchy rash on the hands and feet
The FTA-ABS test might also be done if you’re being treated for another STI or if you’re pregnant. Syphilis can be life-threatening for a growing fetus if it’s left untreated.
You might also need this test if you’re about to get married. This test is required if you want to get a marriage certificate in some states.
There are no special preparations required for an FTA-ABS test. However, you should tell your doctor if you’re taking any blood thinners, such as warfarin (Coumadin). Your doctor may advise you to stop taking certain medications that can affect the test results.
An FTA-ABS test involves giving a small sample of blood. Blood is usually drawn from a vein located on the inside of the elbow. The following will occur:
- Before drawing blood, a healthcare provider will clean the area with a swab of rubbing alcohol to kill any germs.
- They’ll then tie an elastic band around your upper arm, causing your veins to swell with blood.
- Once they find a vein, they’ll insert a sterile needle and draw blood into a tube attached to the needle. You may feel a slight prick when the needle goes in, but the test itself isn’t painful.
- 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.
- Your doctor will follow up with you to discuss the results.
As with any blood test, there’s a small risk of minor bruising at the puncture site. In rare cases, the vein may also 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 also be a problem if you have a bleeding disorder or if you’re taking a blood thinner, such as warfarin or aspirin.
Contact your doctor if you experience any of these symptoms.
A normal test result will give a negative reading for the presence of antibodies to T. pallidum bacteria. This means that you’re not currently infected with syphilis and that you’ve never been infected with the disease.
An abnormal test result will give a positive reading for the presence of antibodies to T. pallidum bacteria. This means that you have or have had a syphilis infection. Your test result will also be positive even if you’ve been previously diagnosed with syphilis and it was treated successfully.
If you’ve tested positive for syphilis, and it’s in the early stages, then the infection can be treated relatively easily. Treatment often involves penicillin injections.
Penicillin is one of the most widely used antibiotics and is usually effective in treating syphilis. You’ll receive a follow-up blood test every three months for the first year and then one year later to ensure the syphilis infection is gone.
Unfortunately, if you have tested positive for syphilis, and the infection in its later stages, then the damage to your organs and tissues is irreversible. This means that treatment is likely to be ineffective.
In rare cases, you may receive a false positive test result for syphilis. This means that antibodies to T. pallidum bacteria were found, but you don’t have syphilis.
Instead, you may have another disease caused by these bacteria, such as yaws or pinta.
Speak with your doctor if you have any concerns about your test results.