Syphilis test (RPR with reflex)

What it measures

RPR measures nontreponemal antibodies, which rise during active infection and fall after treatment. Labs report a reactive RPR as a titer (such as 1:8 or 1:32), and clinicians track that number to see whether treatment worked. Treponemal tests usually stay positive for life, even after a cure. Some labs run the steps in reverse order, starting with the treponemal test, and both approaches are standard.

Who should consider it

• Anyone with a new partner or multiple partners
• People with a sore, a rash on the palms or soles, or other possible symptoms (see a clinician too)
• Anyone whose partner was diagnosed with syphilis
• People who are pregnant, since prenatal care includes syphilis screening
• People taking PrEP or living with HIV, who get tested regularly

How to read your result

• A nonreactive RPR means no sign of active syphilis at the time of the draw. Very early infection can still test negative, so retest if you had a recent exposure.
• A reactive RPR with a positive treponemal test points to current or past syphilis. A clinician sorts out which, often using your history and titer.
• A reactive RPR with a negative treponemal test often means a false positive. Pregnancy, autoimmune disease, and some infections can cause one.
• A positive treponemal test usually stays positive after treatment, so it cannot tell a cured past infection from a new one on its own.

Reference ranges differ between labs. Use the range printed on your own report.

What to do next

If your result points to syphilis, see a clinician or your local health department soon. Penicillin cures syphilis, and early treatment prevents damage to the brain, eyes, heart, and other organs. Partners need testing and treatment too, and health departments can help notify them confidentially. Follow-up RPR titers show whether treatment worked.