Syphilis: Symptoms, Testing and Treatment Explained

RPR stands for Rapid Plasma Reagin. VDRL in testing contexts stands for Venereal Disease Research Laboratory, the institution that developed the original version of this test. Both RPR and VDRL are blood tests that check for certain antibodies your body may produce in response to a syphilis infection.

Neither the RPR nor the VDRL directly detects the syphilis bacterium. Instead, they detect a category of antibodies called reagins that your immune system produces when it encounters infection, which is why a positive result always needs a second, more specific test to confirm.

RPR and VDRL are classified as nontreponemal serologic tests, traditionally used to screen for active syphilis and to monitor how well treatment is working.

Syphilis is a bacterial infection caused by Treponema pallidum. It spreads primarily through direct contact with a syphilis sore during sexual activity, whether vaginal, anal, or oral. Syphilis is contagious, especially in the primary and secondary stages when sores, ulcers, or a rash are present. It can spread even without penetration or ejaculation if any part of the body touches an active sore or rash.

Congenital syphilis occurs when a pregnant woman passes the infection to her baby during pregnancy. This makes antenatal screening particularly important.

One of the reasons syphilis is often missed is that its symptoms shift significantly at each stage, and some stages produce no visible symptoms at all.

Primary Syphilis

During the first (primary) stage of syphilis, you may notice a single sore or multiple sores at the location where syphilis entered your body. The sore usually lasts three to six weeks and heals regardless of whether treatment is received.

Primary syphilis classically presents as a single painless ulcer or chancre at the site of infection, though it can also present with multiple, atypical, or even painful lesions. Because the chancre is painless and often in a hidden location, inside the vagina, rectum, or throat, many people do not notice it.

Secondary Syphilis

During the secondary stage, skin rashes and sores in the mouth, vagina, or anus may appear. The rash typically starts on one or more areas of the body and can appear on the palms of the hands or the soles of the feet.

Secondary syphilis is often marked by a skin rash, swollen lymph nodes, fever, and patchy hair loss, among other symptoms. These symptoms will resolve on their own, but without treatment the infection continues to progress internally.

Latent Syphilis

The latent stage is a period with no visible signs or symptoms whatsoever. Latent syphilis is divided into early latent (infection acquired within the previous 12 months) and late latent. The absence of symptoms does not mean the infection has cleared; it remains detectable through a syphilis test and can still be passed from a pregnant woman to her fetus.

Tertiary Syphilis

Tertiary syphilis is a late symptomatic disease that can manifest months, years, or even decades after the initial infection, presenting as cardiovascular syphilis (such as aortic aneurysm), neurosyphilis (including meningitis, stroke, seizures, and dementia), or gummatous syphilis affecting internal organs.

Between 25% and 40% of all patients with untreated syphilis may eventually develop tertiary disease, though this may take 20 to 30 years to become clinically apparent.

Syphilis diagnosis is a two-step process, and understanding this prevents unnecessary alarm at an initial positive result.

Step 1, Screening (Nontreponemal test): The RPR is a blood test that looks for an antibody called reagin, which the body often produces in response to syphilis infection. The VDRL test can be done on blood or spinal fluid and looks for a broader range of antibodies the immune system might produce in response to syphilis.

Step 2, Confirmation (Treponemal test): If the screening test shows antibodies linked to syphilis infections, a second test is needed to confirm whether syphilis is actually present. This second test looks for antibodies that the immune system makes specifically to fight off syphilis.

A non-reactive result means no antibodies were detected. However, if exposure was very recent, the test may not yet pick up an infection, and a follow-up test may be recommended.

A reactive result means antibodies are present. If an RPR test is positive with a titre greater than 1:8, confirmation by a treponemal test such as TPHA is typically advised. If both tests are positive, treatment is required to avoid further health complications.

An initial reactive RPR result on its own often causes more worry than it should, since the number alone doesn't tell the full story without the confirmatory test to go alongside it.

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A reactive screening result, questions about confirmatory testing, or concerns about a partner's exposure all warrant a direct conversation with a doctor rather than searching for reassurance online. Visit Health's teleconsultation platform connects employees with internal medicine and infectious disease specialists across 30-plus specialties, with general physician consultations typically available within 15 minutes and specialist consultations within 60 minutes.

AI-Powered Smart Reports

An RPR or VDRL report showing a titer value like 1:4 or 1:8 isn't always self-explanatory without context. Visit Health's Smart Reports translate these findings into plain-language summaries, explaining what the titer means and whether a confirmatory test or follow-up is the recommended next step.

What is the full form of RPR in a blood test?

RPR stands for Rapid Plasma Reagin. It is a blood test that screens for antibodies associated with syphilis infection by detecting reagins, non-specific antibodies the immune system produces in response to the infection.

What is the difference between RPR and VDRL?
Both are nontreponemal screening tests for syphilis that detect similar antibodies. The key practical difference is that RPR is performed on plasma without a microscope, making it faster and more suited to high-volume screening. VDRL can be performed on cerebrospinal fluid, making it the standard test for diagnosing neurosyphilis.

What are the first symptoms of syphilis?
The first sign of syphilis is typically a chancre, a small, firm, painless sore, at the site where the bacterium entered the body. It can appear on the genitals, anus, rectum, lips, or throat and typically heals on its own within three to six weeks, with or without treatment.

Can syphilis have no symptoms at all?
Yes. During the latent stage, syphilis produces no visible symptoms at all and can remain undetected for years. This is why routine screening through a syphilis test is important even when no symptoms are present.

What does a reactive RPR test result mean?
A reactive RPR means your blood contains antibodies consistent with a syphilis infection. It does not confirm syphilis on its own; a confirmatory treponemal test is always required. Other conditions can also trigger a reactive result, so the two tests are always interpreted together.

Is a single blood test enough to confirm syphilis?
No. Syphilis diagnosis requires a two-step process: a nontreponemal screening test (RPR or VDRL) followed by a treponemal confirmatory test. A diagnosis should never be made on the basis of a single test result alone.

How long does syphilis treatment take?
For early syphilis, treatment is typically a single injection of benzathine penicillin G. For late latent or tertiary syphilis, three weekly injections are required. Neurosyphilis involves a 10 to 14-day course of intravenous penicillin. Treatment duration is always guided by the stage of infection.

Can syphilis be completely cured?
Yes. Syphilis is caused by a bacterium and responds well to antibiotics, particularly penicillin, when caught early. Early-stage syphilis is straightforward to treat. However, any organ damage caused before treatment began (in tertiary or neurosyphilis cases) may not be reversible, which is why early detection matters.

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