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Syphilis Tests

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Also known as: Venereal Disease Research Laboratory; VDRL; Rapid Plasma Reagin; RPR; Fluorescent Treponemal Antibody Absorption Test; FTA-ABS; Treponema pallidum Particle Agglutination Assay; TPPA; Microhemagglutination Assay; MHA-TP; Darkfield Microscopy; Automated Immunoassays for Syphilis Antibodies; Treponema pallidum by PCR
Formal name: Syphilis Detection Tests

The Test Sample

What is being tested?

Syphilis is an infection caused by the bacteria Treponema pallidum that is most often spread by sexual contact, such as through direct contact with a syphilis sore (chancre), a firm, raised, painless sore. The most common syphilis tests detect antibodies in the blood that are produced in response to a T. pallidum infection. Some methods that are used less commonly directly detect the bacteria or its genetic material (DNA).

Syphilis is easily treated but can cause severe health problems if left untreated. An infected mother can also pass the disease to her unborn child, with serious and potentially fatal consequences for the baby. (See Common Questions #3)

There are several possible stages with syphilis:

  • Primary syphilis—the primary stage begins about 2-3 weeks after being infected. One or more chancres appear, usually on the part of the body exposed to the sexual partner's chancre, such as on the penis or vagina. However, the chancre is usually painless and may go unnoticed, especially if it is in the rectum or on the cervix, and disappears within 4-6 weeks, healing regardless of whether the infected person is treated or not.
  • Secondary syphilis—if primary syphilis is left untreated, secondary syphilis may occur from 6 weeks to 6 months after the chancre first appears. It is marked by a skin rash that often is rough, red, and spotted, appearing frequently on the palms of the hands and the bottoms of the feet (an unusual place for most other causes of rashes) and that usually does not itch. There may be other symptoms as well, such as fever, fatigue, swollen lymph nodes ("glands"), sore throat, and body aches.
  • Late, tertiary syphilis—if untreated, secondary syphilis may continue into a latent stage, during which an infected person has no symptoms but continues to have the infection, and this stage can last for years. If still untreated, about 15% of people will develop the complications of late, or tertiary, syphilis. In these cases, the bacteria can damage the heart, eyes, brain, nervous system, bones, joints, or almost any other part of the body. When the central nervous system is affected, it is called neurosyphilis. Tertiary syphilis can last for years, with the final stage leading to mental illness, blindness, other neurological problems, heart disease, and death.

Syphilis is most infectious during the primary and secondary stages. In 2011, about one-third of over 46,000 new cases of syphilis reported to the Centers for Disease Control and Prevention (CDC) were primary or secondary stage syphilis. Seventy-two percent of these cases were among men who have sex with men.

Syphilis can be treated with antibiotics, preferably penicillin. Newly acquired infections can be cured easily; however, longer treatment may be needed for someone who has been infected for more than a year.

How is the sample collected for testing?

Depending on the stage of disease and test method used, different samples are needed:

  • Most often, blood is drawn from a vein in the arm to test for antibodies.
  • If a syphilis sore is present, a health care provider may take a scraping from the chancre on the affected area, such as the cervix, penis, anus, or throat.
  • If someone has late or latent stages of the disease with suspected brain involvement (neurosyphilis), the doctor will perform a spinal tap to check the cerebrospinal fluid (CSF) for infection.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.