What is syphilis, and can a blood test detect it?

Syphilis is a common but serious sexually transmitted disease (STD) caused by the bacterium, Treponema pallidum. When a person has direct physical contact with another person who has a syphilitic sore or lesion, more commonly known as a chancre, there is a likelihood of transmission. Initially painless and circular, chancres can be found on or around the external genitals, in the vagina, or around the anus. They can also appear in the rectum and in or around the mouth. 

The most common transmission of syphilis is through anal, vaginal, or oral sex with a partner. If a person has a minor cut or abrasions on the surface of the skin, the bacteria find their way of entering the body through that opening. They can also enter through mucous membranes. Pregnant women who have the syphilis infection are also prone to transmit the infection to their unborn child. The baby is then susceptible to birth deformities, stillbirth, or death. Sharing the same toilet, tubs, clothes, or eating utensils will not result in a person contracting syphilis.

Symptoms of syphilis can resemble other diseases; therefore, a person may think he or she has gonorrhea. However, syphilis is a disease that progresses through four stages, each separated by months and can even range in years, depending on how soon the person seeks treatment.

Primary stage
A single, small chancre appears, although there may be multiple sores. It is painless, round, and firm and appears where the bacteria entered the body. Nearby lymph nodes may enlarge but are not painful. The chancre lasts three to six weeks and heals, whether a person is treated or not.

Secondary stage

Secondary symptoms appear, weeks or even months later, when microbes spread to tissues and organs. Non-painful skin rashes keep appearing and disappearing on one or more areas of the body for as long as a year. Sometimes these rashes are in association with fever, headache, muscle aches, sore throat, weakness or discomfort throughout the body, swollen lymph nodes and patchy hair loss. The rash, which is usually not itchy, appears on the soles of the feet and palms of the hands as rough, red or reddish-brown spots. 

Latent stage

If not treated, the disease can progress to the latent (hidden) stage, where the secondary stage rash goes away and there are no symptoms. A person may experience this period as short-term as one year. Others may feel asymptomatic from 5 to 20 years. A person is still contagious during the earlier part of this stage. 

Tertiary stage

Complications will develop in about 15-30% of people who don’t seek treatment and therefore this stage may start as early as one year after a person has been infected. Tertiary syphilis takes three forms: cardiovascular, which severely affects the heart; neurosyphilis, which affects the brain and the nervous system, in addition to the eye (ocular syphilis); and benign late syphilis. Nervous system symptoms include neck stiffness, headaches, irritability, and paralysis. Damage may also be done to the blood vessels, liver, bones, and joints. Tertiary lesions may destroy normal skin, bone, and joints by ulceration. 

Syphilis is difficult to diagnose, therefore a series of blood tests are often necessary. The body produces antibodies in the immune system to fight foreign substances, such as the bacteria that cause syphilis. A syphilis blood test can confirm whether or not the body has these antibodies.

The body houses these antibodies for years, so a syphilis test is able to determine whether the infection is current or if it is from a prior infection.  

Two common syphilis blood screening tests that help diagnose the disease in the early stages of infection include: Rapid plasma regain (RPR) and Venereal disease research laboratory (VDRL). Both tests look for the antibodies to the syphilis bacteria and have an expected turnaround time of 1-5 days for results. As mentioned before, a series of blood tests is necessary, so if a screening test returns positive you will need additional testing to dismiss or verify a syphilis diagnosis.

A blood test usually takes less than five minutes when a health care professional draws a blood sample intravenously, from a vein in the arm. This can be done in a doctor’s office or a service like Walk-in Lab. If the result is negative, doctors may ask you to wait a few weeks before returning for another test. This is because the RPR test has the potential for a false-negative result. The same goes for the VDRL test, where false-negative results can be produced if you have had syphilis for less than three months.

The following tests are used to confirm syphilis:


  • Enzyme immunoassay (EIA) test
  • Fluorescent treponemal antibody absorption (FTA-ABS) test


      • Can be used to find syphilis except during the first 3-4 weeks after exposure
      • Can also be done on a sample of spinal fluid


  • Darkfield microscopy


    • A special microscope searches for the syphilis-specific germ in a sample of fluid or tissue from an open sore
    • Primarily diagnoses in an early stage
    • Less commonly performed

Syphilis can be cured in its early stages. However, it does not protect you from getting it again and there is still a chance of reinfection even after successful treatment. When doctors test for syphilis, they usually prescribe antibiotics to treat the infection, such as penicillin. Syphilis is not just a one-time only thing. Using condoms and/or dental dams and getting tested regularly can help prevent the infection.

Syphilis is troublesome in which the signs could be so mild that they’re unnoticeable. They can be confused with being just pimples or rashes. Three weeks after a person has been exposed to the infection, he or she can develop the painless chancre sore from 10 to 90 days but is still highly contagious to others. A person can have syphilis without showing symptoms for years. 

Syphilis can be transmitted orally. The most common transmission is through oral sex, both giving and receiving. 

Walk-In Lab offers STD blood tests that you can order from the privacy of your own home.  These services are designed to empower people to access STD screening when they are reluctant to discuss with their healthcare provider directly about the topics of sex or STDs for fear of stigma and being judged.  RPR Syphilis Blood tests start at $43 and the STD test packages start at $139. These tests are FDA-approved and CLIA-certified and take about five minutes to do. In addition to syphilis tests, the packages include tests for chlamydia and gonorrhea, trichomonas, hepatitis B and C, and human immunodeficiency virus (HIV)

In conclusion, if diagnosed with syphilis, it is important to tell your sexual partner so that he or she can get tested and treated immediately. Discovering that you have contracted syphilis can be very upsetting, angering, and you may even feel ashamed that you might have infected others. A reluctance to discuss infection risk with healthcare providers should not stop you from accessing an at-home STD test. Prepare for your appointment with your doctor to get the right care and avoid sex or follow safe sex practices.


  1. https://www.mayoclinic.org/diseases-conditions/syphilis/symptoms-causes/syc-20351756
  2. https://www.cdc.gov/std/syphilis/stdfact-syphilis.htm
  3. https://www.healthline.com/health/std/syphilis
  4. https://www.nhs.uk/conditions/syphilis/
  5. https://www.plannedparenthood.org/learn/stds-hiv-safer-sex/syphilis/how-do-i-get-treated-for-syphilis
  6. https://healthy.kaiserpermanente.org/health-wellness/health-encyclopedia/he.syphilis.hw195071
  7. https://www.uofmhealth.org/health-library/hw5839#hw5842
  8. https://medlineplus.gov/syphilis.html


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