Syphilis symptoms
A syphilis infection is associated with certain signs and symptoms based on the phase of the infection:
- The earliest stage (or "primary syphilis"), is associated with a firm, round, painless sore on the genitals. The sore, called a “chancre,” usually goes away after several weeks, even if the infection isn’t treated.
- Untreated syphilis can advance to a secondary syphilis stage of infection, which can be characterized by skin rashes, fever, patchy hair loss, headaches, muscle aches, fatigue, and other symptoms.
- The latent stage is the next stage of an untreated syphilis infection. Latent syphilis often occurs without obvious signs or symptoms, but that doesn’t mean the infection has gone away. On the contrary, during the latent syphilis stage, the infection persists in the body—sometimes for years—and can ultimately lead to tertiary syphilis, which damages organ systems like the nervous system, heart, and eyes.
Neurosyphilis
In some cases, syphilis bacteria can attack the nervous system—resulting in “neurosyphilis.” Neurosyphilis—a condition that can develop at any point in a syphilis infection—can lead to severe brain disorders characterized by dementia, loss of muscle coordination, and more.
Because the signs and symptoms of neurosyphilis are similar to those of other disorders, a diagnosis requires lab testing via a lumbar puncture—or “spinal tap" (so spinal fluid can be analyzed).
More specifically, in a lumbar puncture, a needle extracts a sample of cerebrospinal fluid from the spinal cord (the system of nerves and vertebrae that runs down the back and transmits signals between the brain and the rest of the body). The cerebrospinal fluid is then checked for syphilis bacteria to determine if the infection has reached the nervous system.
Syphilis diagnosis
Two types of syphilis tests can screen for and diagnose syphilis (along with consideration of signs and symptoms potentially caused by this sexually transmitted disease). Syphilis testing can be done with a treponemal test or a non-treponemal test. Both syphilis tests are required to confirm a diagnosis.
Treponemal tests
Treponemal tests check blood samples for antibodies that react with certain molecules (syphilis antigens) that are unique to the syphilis bacterium. (Antibodies are specific compounds made by your body in response to bacterial infections, viruses, or other microbes. They help tag foreign pathogens for destruction by the body’s immune cells.)
The Everlywell Syphilis Test—which lets you check for syphilis antibodies from the privacy and convenience of home—is a treponemal test.
Non-treponemal tests
Non-treponemal tests are some of the oldest antibody tests that check for syphilis antibodies, and are widely used by many laboratories since they are needed for diagnosing an infection.
During an active infection, syphilis bacteria produce a very specific compound known as “cardiolipin-lecithin-cholesterol.” In response, your immune system makes antibodies that react with this compound that tell your immune system’s defender cells where the infection is taking place in the body.
Non-treponemal tests measure how much, if any, of these syphilis antibodies are in a blood test sample. The Rapid Plasma Reagin antibody test (or RPR test) and Venereal Disease Research Laboratory test (also known as a VDRL test) are some of the most commonly used. Both the RPR test and VDRL test evaluate antibodies in your blood to determine if you have been infected with bacteria that cause syphilis.
What’s the difference between a treponemal and nontreponemal test?
Treponemal tests give either a “positive” or “negative” result. Treponemal tests are often used as screening tests, where a positive result indicates that additional testing for syphilis is needed to confirm the diagnosis.
Non-treponemal tests can give a numerical result because these tests measure the amount of antibodies that react with syphilis bacteria compounds. This makes non-treponemal tests useful for determining what stage the infection is in—and how the infection responds to treatment (based on the amount of antibodies in the blood sample).
What about rapid testing for syphilis?
In certain specific clinical situations, rapid tests that check for syphilis and give results in 10 to 15 minutes may be used, but additional syphilis testing with a nontreponemal test is needed for a diagnosis (in the event of a positive result on the rapid test).