Syphilis Tests
Reviewed
Also called: rapid plasma reagin (RPR), Venereal Disease Research Laboratory (VDRL), fluorescent treponemal antibody absorption (FTA-ABS) test, agglutination assay (TP-PA), darkfield microscopy, Treponema pallidum particle agglutination assay (TP-PA)
Syphilis tests generally look for certain antibodies in your blood. Testing usually involves two steps.
Specimen: Blood or cerebrospinal fluid (CSF)
Why this test may be ordered
- You have symptoms of syphilis (e.g., painless sore, rash, fever, swollen glands).
- Your sexual partner was recently diagnosed with syphilis.
- You are at high risk (multiple partners, unprotected sex, HIV, MSM, other STIs).
- You are pregnant (CDC recommends testing at first prenatal visit, and again at 28 weeks and delivery if at high risk).
Preparation and collection
You don't need any special preparations for a syphilis blood test. For a lumbar puncture, you may be asked to empty your bladder (pee) and bowels (poop) before the test.
A syphilis test is usually a blood test. During a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. If your symptoms show that syphilis may be affecting your brain and nervous system, your provider may order a syphilis test of your cerebrospinal fluid (CSF).
There is very little risk to having a blood test. With a spinal tap, there is also very little risk. After the test, you may feel some pain or tenderness in your back or have some bleeding where the needle was inserted. You may also get a headache.
Understanding results
Blood tests cannot tell the difference between syphilis and their related bacteria.
- Screening test negative: If your screening test results are negative (normal), it means you probably don't have a syphilis infection. Limitation: However, it doesn't completely rule out the possibility. Antibodies can take a couple of weeks to develop. Next step: So, you may need another screening test if you think you were exposed to syphilis.
- Screening test positive: If your screening test results are positive, it means you have antibodies that may be from a syphilis infection. Limitation: Blood tests cannot tell the difference between syphilis and their related bacteria. Next step: Your provider will likely order a second test to confirm whether or not you have syphilis.
- Follow-up test confirms syphilis: If your follow-up test confirms you have syphilis, you will probably be treated with penicillin, a type of antibiotic. Limitation: Later-stage syphilis is also treated with antibiotics, but this treatment can't undo any damage that the syphilis caused. Next step: You will likely need repeat syphilis screening tests to see how well your treatment is working.
- Screening tests may be negative early after infection because antibodies take a few weeks to develop.
- A positive screening test does not confirm syphilis; a confirmatory test is required.
- Confirmatory blood tests cannot distinguish between a current and a past treated syphilis infection.
- Blood tests cannot tell the difference between syphilis and related infections (yaws, bejel, pinta).
- At-home kits are screening only; a confirmatory test is still needed.
What to do next
If you are diagnosed with syphilis, you need to tell anyone you've had sexual contact with so that they can get tested and treated if necessary. Avoid sexual contact with others until testing shows you are cured.
- Do I need to be tested for syphilis?
- What do my results mean?
- Do I need a confirmatory test?
- What should I do if I have syphilis?
- How can I prevent spreading syphilis?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.