Syphilis III: Beyond a Positive Test
A positive syphilis test needs to be interpreted in context. Test type, symptoms, medical history and previous treatment help determine the stage and guide treatment and follow-up.
Syphilis II: The silent infection Click here to find out more
Syphilis I: The great imitator Click here to find out more
Understanding Syphilis Blood Tests
| Test | What it shows | How it is used |
|---|---|---|
| TPPA / TPHA | Antibodies specific to the bacteria that cause syphilis | Usually remains positive for many years, often for life. It cannot show whether treatment has worked. |
| RPR / VDRL | Antibody activity reported as a titre, such as 1:4, 1:8, or 1:32 | Used to assess disease activity and monitor the response to treatment. |
A titre is a number used to track changes over time.
TPPA and TPHA detect syphilis - specific antibodies, while RPR and VDRL titres help assess the infection and monitor the response to treatment. Both types of tests should be interpreted together.
From a Positive Result to a Diagnosis
A positive screening result is only the starting point. To confirm the diagnosis and determine the stage of infection, your doctor will:
- Consider any symptoms, both past and present
- Check for any history of syphilis testing or treatment
- Assess when the infection may have occurred
- Perform a clinical examination if needed
If you have neurological, visual, or hearing symptoms, further tests may be needed to assess for neurosyphilis, ocular syphilis, or otosyphilis.
Treatment and Follow-Up
Syphilis is curable, and penicillin is the preferred treatment. The treatment schedule depends on the stage and likely duration of the infection. Other options may be considered for people with a penicillin allergy.
Follow-up RPR or VDRL tests track changes in the titre. TPPA and TPHA often remain positive after successful treatment, while RPR or VDRL may remain at a low level.
Regular follow-up as advised by your doctor is important to confirm that treatment has worked and to detect possible reinfection.
Reinfection Is Possible
Having syphilis once does not provide immunity, so reinfection is possible even after successful treatment.
For people previously treated for syphilis, changes in the RPR or VDRL titre are more useful for identifying reinfection than a positive TPPA or TPHA result.
Syphilis is curable, but treatment and follow-up go together. Completing treatment, returning for blood tests, and ensuring partners are assessed help protect your health and the health of others.
