Syphilis Tests

Syphilis tests check for antibodies in your blood or spinal fluid to detect the bacterium that causes syphilis, a common sexually transmitted infection.

What are syphilis tests?

Testing generally occurs in two steps. The first step is a screening test to identify antibodies produced in response to syphilis, autoimmune diseases, or other infections. Common screening tests include:

• Rapid plasma reagin (RPR): A blood test looking for an antibody called reagin.
• Venereal Disease Research Laboratory (VDRL) test: Can be performed on blood or spinal fluid to look for a broad range of antibodies.

If the screening is positive, a second, confirmatory test is required. This test looks for antibodies specific to the syphilis bacterium to confirm a current or past infection.

Why do I need syphilis tests?

You should get tested if you have symptoms or if a sexual partner has been diagnosed with syphilis. Syphilis progresses in four stages:

• First stage: A small, painless sore (chancre) appears 2–12 weeks after exposure.
• Second stage: Symptoms include fever, swollen glands, a rough red rash (often on palms or soles), headache, muscle aches, sore throat, fatigue, weight loss, or patchy hair loss.
• Third (latent) stage: No symptoms, but the infection persists and can cause damage.
• Fourth stage: Severe symptoms years later, including dementia, blindness, deep bone pain, numbness, dizziness, heart damage, and hearing loss.

Regular testing is recommended for those at high risk, including individuals with multiple sex partners, those who have unprotected sex, or those with HIV or other STIs. Pregnant individuals should be tested at their first prenatal visit, and again at 28 weeks and at delivery if they are at higher risk.

What happens during a syphilis test?

Most tests involve a standard blood draw. If the infection is suspected to have affected the brain or nervous system, a provider may perform a spinal tap (lumbar puncture) to collect cerebrospinal fluid (CSF). During a spinal tap, a provider injects an anesthetic into the lower back and inserts a needle between the vertebrae to withdraw a small amount of fluid.

Will I need to do anything to prepare for the test?

No special preparation is needed for a blood test. For a lumbar puncture, you may be asked to empty your bladder and bowels beforehand.

Are there any risks to the test?

Blood tests carry minimal risk, such as slight pain or bruising. A spinal tap may cause back pain, tenderness, or a headache that can last for several days.

What do the results mean?

• Negative: You likely do not have syphilis, though early infections may not yet show antibodies.
• Positive: You have antibodies that may indicate syphilis. A follow-up test is required to confirm.

If confirmed, syphilis is treated with antibiotics, such as penicillin. While antibiotics cure the infection, they cannot reverse damage caused by late-stage syphilis.