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To screen for or diagnose an infection with the bacterium Treponema pallidum, which causes syphilis, a sexually transmitted disease (STD)
When you have symptoms of a syphilis infection; when you are at risk of being exposed to syphilis, such as when you have another STD or HIV infection, are a man who has sex with men, have a sexual partner diagnosed with syphilis, or have engaged in high-risk sexual activity; when you are pregnant
Most often, a blood sample drawn from a vein in your arm; sometimes, a scraping from a chancre in the affected area; less commonly, cerebrospinal fluid taken via a spinal tap, depending on your clinical presentation
Syphilis is an infection caused by the bacterium 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 bacterium or its genetic material (DNA).
Syphilis is easily treated with antibiotics 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 below)
There are several possible stages with syphilis:
Syphilis is most infectious during the primary and secondary stages. In 2014, about one-third of over 63,000 new cases of syphilis reported to the Centers for Disease Control and Prevention (CDC) were primary or secondary stage syphilis. Eighty-three 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.
Depending on the stage of disease and test method used, different samples are needed:
Syphilis tests are used to screen for and/or diagnose infection with Treponema pallidum, the bacterium that causes syphilis.
Several different types of tests are available. Antibody tests are most commonly used.
Antibody tests (serology)—these tests detect antibodies in the blood and sometimes in the cerebrospinal fluid (CSF). Two general types are available for syphilis testing, nontreponemal antibody test and treponemal antibody test (derived from the name of the bacterium). Either type may be used for syphilis screening but must be followed by a second test that uses a different method to confirm a positive result and to diagnose active syphilis:
Direct detection of bacteria—these tests are less commonly performed:
|Stages of disease:||Exposure to bacteria||Chancre, "Primary syphilis"||Skin eruptions, "Secondary syphilis"||Neurological disease, "Tertiary syphilis"|
|The time after exposure that these stages may occur if the person is not treated||Day 1||10-90 days||6 weeks to 6 months||10-30 years|
|Description||Transmission of syphilis occurs during vaginal, anal, or oral sex. Pregnant women with the disease can transmit it to unborn child. First-time infection provides no immunity; re-infection can occur if exposed again.||Appearance of a single sore, though there may be multiple sores at the location(s) where the bacteria entered the body. The sore is usually firm, round, and painless and can easily go unnoticed. It lasts 3-6 weeks and heals regardless of whether or not the person is treated.||Rash on one or more areas of the body can appear from the time when the primary sore is healing to several weeks after the sore has healed. Rash usually does not itch and is unusual in that it can occur on palms of hands and soles of feet.||Skin lesions or nodules called granulomas (gummas) appear, degenerative changes in CNS (numbness, paralysis, gradual blindness, dementia), and cardiovascular lesions|
|Nontreponemal Antibody Tests: VDRL and RPR.||Used to screen or confirm a positive treponemal antibody test; used to guide treatment.||Highly sensitive; positive screening results must be confirmed with a treponemal antibody test as it may be positive in other conditions. Nontreponemal antibodies typically disappear in an adequately treated person after about 3 years.||Same as primary stage||VDRL is primarily performed on CSF and used to detect neurosyphilis.|
|Treponemal Antibody Tests: FTA-ABS, TP-PA, immunoassays (IA).||Used to screen or confirm a positive nontreponemal antibody test.||Highly specific; positive screening results must be followed by nontreponemal antibody test to differentiate between active and past infection. These antibodies remain positive for life even after treatment.||Same as primary stage||The CSF FTA-ABS is less specific than VDRL, but the test is highly sensitive; can be used to exclude neurosyphilis.|
|Direct detection tests||Used much less commonly|
|Microscopic Exam, Darkfield Exam||Sample from chancre is placed on a slide, examined with a special microscope.||If the bacteria are seen, a definitive diagnosis of syphilis is made.||Not applicable||Not applicable|
|Polymerase chain reaction (PCR)||Molecular method; also called nucleic acid amplification test or NAAT||Detects genetic material of bacteria in sample from chancre||Detects genetic material of bacteria in blood||Detects genetic material of bacteria in blood and/or CSF sample|
A syphilis test may be ordered when a person has signs and symptoms, such as:
Screening for syphilis is recommended, regardless of symptoms, when a person:
The CDC recommends follow-up testing, such as measuring the level of antibodies (e.g., RPR titers), when a person has been treated for syphilis to be sure that treatment is successful and the infection cured.
Care must be taken when interpreting results from tests for syphilis.
A negative blood test means that it is likely that no infection is present. However, a negative screening test means only that there is no evidence of disease at the time of the test. Antibodies may not be detected for several weeks after exposure to the bacteria. If a person knows he or she has been exposed, or if suspicion of infection remains high, then repeat testing at a later date may be required. It is also important for those who are at increased risk of syphilis infection to have screening tests performed regularly to check for possible infection.
A positive RPR or VDRL screen must be followed by a specific treponemal antibody test (e.g., FTA-ABS, TP-PA):
Alternatively, a healthcare practitioner or laboratory will use a treponemal antibody test (FTA-ABS, TP-PA, IA) as an initial test. A positive result indicates the presence of syphilis antibodies in the blood, but since treponemal antibodies remain positive even after an infection has been treated, it does not indicate whether the person has a current infection or was infected in the past. Conversely, nontreponemal antibodies as detected with an RPR typically disappear in an adequately treated person after about 3 years. Thus, if an initial treponemal test is positive, an RPR can be performed to differentiate between an active or past infection. In this case, a positive RPR would confirm that the person has been exposed to syphilis and, if not treated previously, has an active infection or, if treatment had occurred more than 3 years ago, possible re-infection.
For monitoring treatment and/or determining if treatment was successful, the results of one or more RPR titers may be evaluated. Syphilis antibodies should be lower following treatment. For example, if the RPR was initially reported as 1:256, a value of 1:16 after treatment would indicate a lower level of antibody. If the titer remains the same or rises, the affected person may have a persistent infection or was reinfected. Results may also be expressed as dilutions (e.g., 1/16) or converted to a whole number (e.g., 16 dils).
Results of syphilis tests performed on CSF samples, usually when someone has late or latent stages of the disease with suspected brain involvement (neurosyphilis), are often interpreted in conjunction with a blood test as well as the affected person's signs, symptoms, and medical history.
A positive VDRL or FTA-ABS result on a sample of CSF indicates likely infection of the central nervous system. A negative result, especially on an FTA-ABS, may help to rule out infection of the central nervous system.
If a scraping from a suspected syphilis sore reveals presence of the syphilis bacteria (a positive test on either darkfield microscopy or PCR), the person being tested has an infection that requires treatment with a course of antibiotics, preferably penicillin.
A negative result from a scraping may mean that there is no syphilis infection present and symptoms are due to another cause or that there were insufficient bacteria present in the sample to be detected.
After successful treatment, nontreponemal antibodies disappear over time; treponemal antibodies are present in the blood for life.
The different tests available to screen for and diagnose syphilis vary in their accuracy depending on the stage of disease.
If you are sexually active, you should consult a healthcare practitioner about any suspicious rash or sore in the genital area; there are many other sexually transmitted diseases besides syphilis. If you are infected, tell your sexual partner(s) to get tested and treated.
The risk of contracting other STDs increases if you have syphilis sores. You are 2 to 5 times more likely to be infected with HIV, if exposed, when syphilis sores are present, according to the Centers for Disease Control and Prevention. If you have such chancres and have not been diagnosed with HIV, you should be tested for HIV.
Samples are typically sent to a laboratory and results could take 3-5 days.
The most reliable ways to avoid infection with syphilis or any sexually transmitted disease are to abstain from oral, vaginal, and anal sex or to be in a long-term, mutually monogamous relationship with an uninfected partner. People who are sexually active should correctly and consistently use condoms to reduce the risk of infection with syphilis and other STDs.
Syphilis in pregnancy can cause many health problems for the infant, including low birth weight, premature delivery, and even stillbirth. In 2014, the U.S. Centers for Disease Control and Prevention (CDC) received 458 reports of syphilis cases in children who contracted syphilis from their mothers, known as congenital syphilis. Sometimes newborns with syphilis may not have signs of the disease. However, without immediate treatment, the newborn could develop cataracts, deafness, or seizures. According to the American Sexual Health Association, many cases of congenital syphilis go unnoticed until symptoms appear in childhood or adolescence.
The CDC and the U.S. Preventive Services Task Force recommend that pregnant women be tested for syphilis, preferably at the first prenatal visit. The CDC also recommends testing during the third trimester for higher risk women.
Visit the CDC webpage Get Tested to find out where you can get tested. You can input your zip code and find a local testing site.
Yes, you should tell your sexual partner(s) that you have syphilis so they can get tested and treated.
Yes. Even though treatment will cure your infection, you can get it again if you are exposed again.
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