Syphilis Tests
Reviewed
Syphilis tests are used to screen for and diagnose syphilis, a sexually transmitted infection. Testing usually involves a screening blood test (RPR or VDRL) followed by a confirmatory blood test (FTA-ABS, TP-PA, etc.). If symptoms suggest brain or nervous system involvement, a cerebrospinal fluid test may be done. Screening tests look for antibodies that may be from syphilis; confirmatory tests look for antibodies specific to syphilis. A positive confirmatory test indicates a current or past syphilis infection. Treatment with antibiotics is effective, especially in early stages.
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 and bowels before the test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- 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 have a positive confirmatory test, you will likely be treated with antibiotics. You should inform any sexual partners so they can be tested. Repeat screening tests may be needed to monitor treatment effectiveness. Avoid sexual contact until treatment is complete.