The test is used to diagnose infection with syphilis.

A doctor may request the test:

• when a chancre (ulcer or sore) is present on the genitals or throat
• if a patient is being treated for another sexually transmitted disease, such as gonorrhoea
• if a patient is thought to be an at risk group
• as part of screening before or during pregnancy, because untreated syphilis can infect and even kill a developing fetus or
• if a patient complains of non-specific symptoms that resemble those of syphilis, to determine the exact cause of the illness.

The blood test detects the antibodies that the body produces to combat infection, so a positive test indicates that you have either a current or past infection. Results of RPR and VDRL tests are reported as reactive with a dilutional titre given as a number . The degree of titre elevation is not necessarily reliable for staging syphilis, but appropriate titre decline does define a successfully treated case. The blood test becomes positive 3-6 weeks after exposure to the bacteria but might not find antibodies for up to 90 days after infection. In addition, the antibodies remain in the body for years, so if one has had a past infection with syphilis and was treated, the test results could remain positive for life. If you have a past history of treated syphilis infection, this information should be shared with your doctor. This will ensure selection of the appropriate tests to determine whether or not current infection is present.

The PCR test detects Treponema pallidum DNA if it is present. A positive test indicates that you have a current infection.

Some syphilis tests are not very specific and may occasionally give a false positive result. The tesing is performed in stages. A very sensitive screening test is performed first, with more speific tests performed if the  screening test is positive. Any positive tests should be checked by another test. If there is concern about their validity, testing another sample is reasonable. Occasional biological false-positives occur in the settings of pregnancy, injecting drug use, acute viral infections, and autoimmune disease.

Sexual partner(s) of patients with syphilis must get tested and treated.

People with syphilis often have higher risk for contracting other sexually transmitted diseases, including the risk of being infected with HIV, the virus that causes AIDS. HIV infected patients often show poor antibody response to infection and rapidly progress to late stages of the disease.

The first symptoms of syphilis may not be seen immediately. The primary stage begins within 10 days to three months of being infected. A sore appears, called a chancre, usually on the part of the body exposed the partner’s ulcer, such as the penis or vagina. The chancre may be painless and go unnoticed, and it heals within a few weeks. About 50% of people will have no symptoms.

Secondary syphilis begins three to six weeks after the chancre appears. It is marked by a skin rash that usually heals in several weeks or months. There may be other symptoms as well, such as fever and sore throat. If untreated, syphilis may continue into a latent stage, during which you have no symptoms and are no longer contagious. However, about one-third of untreated cases will advance into 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. This stage can last for years, with the final stage leading to mental illness, blindness, other neurological problems, heart disease, and death. Syphilis infection can be much more persistent and potentially more serious if the patient is HIV positive.

The bacterium is passed on through direct contact with a syphilis sore. This generally happens through sexual contact, such as vaginal, anal, or oral sex. An infected pregnant woman can spread the disease to her fetus, with serious and potentially fatal consequences for the baby.

Syphilis can be treated with the antibiotic penicillin. Newly acquired infections can be cured easily. A longer treatment is needed to cure someone who has been infected for more than two years or if the timing of infection is unknown. A previously treated person can become infected with syphilis a second time if exposed again.

Sexually active young men and women can reduce their risk of syphilis by reducing their numbers of partners and using condoms correctly and consistently during sexual intercourse.