30/06/2016
The syphilis tests.
How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?
How is it used?
Syphilis tests are used to screen for and/or diagnose infection with Treponema pallidum, the bacterium that causes syphilis. For more details about syphilis infection, see the "What is being tested?" section.
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:
Nontreponemal antibody tests--these tests are called "nontreponemal" because they detect antibodies that are not specifically directed against the Treponema pallidum bacterium. These antibodies are produced by the body when an individual has syphilis but may also be produced in several other conditions. The tests are highly sensitive but, since they are non-specific, false-positive results can be caused by, for example, IV drug use, pregnancy, Lyme disease, certain types of pneumonia, malaria, tuberculosis, or certain autoimmune disorders including lupus. A positive screening result must be confirmed with a more specific (treponemal) test. Nontreponemal tests include:
RPR (Rapid Plasma Reagin)--in addition to screening, this test is useful in monitoring treatment for syphilis. For this purpose, the level (titer) of antibody is measured. It may also be used to confirm the presence of an active infection when an initial test for treponemal antibodies is positive (see below).
VDRL (Venereal Disease Research Laboratory)--in addition to blood, this test is primarily performed on CSF to help diagnose neurosyphilis.
Treponemal antibody tests--these blood tests detect antibodies that specifically target T. pallidum. They are highly specific for syphilis, meaning other conditions are unlikely to cause a positive result. However, once a person is infected and these antibodies develop, they remain in the blood for life. By comparison, nontreponemal antibodies typically disappear in an adequately treated person after about 3 years. Therefore, a positive treponemal screening result must be followed by a nontreponemal test (such as RPR) to differentiate between an active infection (or reinfection) and one that occurred in the past and was successfully treated. Treponemal antibody tests include:
FTA-ABS (Fluorescent treponemal antibody absorption)--this test is useful after the first 3-4 weeks following exposure. In addition to blood testing, it can be used to measure antibodies to T. pallidum in the CSF to help diagnose neurosyphilis.
TP-PA (T. pallidum particle agglutination assay)--this test is sometimes performed instead of FTA-ABS because it is more specific and there are fewer false positives.
MHA-TP (Microhemagglutination assay)--another confirmatory method; this test is used much less commonly now.
Immunoassays (IA)--in more recent years, several automated tests have been developed, making them convenient for screening purposes.
Direct detection of bacteria—these tests are less commonly performed:
Darkfield microscopy--this method may be used in the early stages of syphilis when a suspected syphilis sore (chancre) is present. It involves obtaining a scraping of the sore, placing it on a slide, and examining it with a special instrument called a dark-field microscope.
Molecular testing (polymerase chain reaction, PCR)--this test detects genetic material from the bacteria in the sample from the sore, in blood, or in CSF.
Expand TableSyphilis Tests
The following table summarizes the stages of syphilis and types of tests that may be used:
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, a**l, or oral s*x. 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
Antibody tests:
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 (much less common):
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) 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
When is it ordered?
A syphilis test may be ordered when a person has signs and symptoms, such as:
A chancre on the ge****ls or throat
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, with or without other symptoms, such as fever, fatigue, swollen lymph nodes ("glands"), sore throat, and body aches
Screening for syphilis is recommended, regardless of symptoms, when a person:
Is being treated for another s*xually transmitted disease, such as gonorrhea
Is pregnant, during the first prenatal visit and again in the third trimester and at delivery if the woman is at high risk
Is a man who has s*x with men; testing should be done at least yearly or every 3-6 months if at high risk
Engages in high-risk s*xual activity, such as having unprotected s*x with multiple partners
Has HIV infection, when first diagnosed and then at least yearly; may be done more frequently if at high risk
Has one or more partners who have tested positive for syphilis
Has been informed by public health officials that he or she has been exposed to an infected partner
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.
What does the test result mean?
Care must be taken when interpreting results from tests for syphilis.
Antibody tests:
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):
A positive result on the second method confirms the screening result and the affected person is diagnosed with syphilis.
A negative result on the treponemal test may mean that the initial RPR or VDRL test was falsely positive. Further testing and investigation may be done to determine the cause of the false positive.
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).
CSF tests:
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.
Direct detection:
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.
Is there anything else I should know?
The different tests available to screen for and diagnose syphilis vary in their accuracy depending on the stage of disease.
If you are s*xually active, you should consult a healthcare practitioner about any suspicious rash or sore in the ge***al area; there are many other s*xually transmitted diseases besides syphilis. If you are infected, tell your s*xual 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.
Common Questions
How long does it take to get results from a syphilis test?
How can syphilis be prevented?
Why is having syphilis a problem during pregnancy?
Where can I get tested?
Should I tell my partner that I have syphilis?
If I get treated, can I get syphilis again?
1. How long does it take to get results from a syphilis test?
Samples are typically sent to a laboratory and results could take 3-5 days.
2. How can syphilis be prevented?
The most reliable ways to avoid infection with syphilis or any s*xually transmitted disease are to abstain from oral, vaginal, and a**l s*x or to be in a long-term, mutually monogamous relationship with an uninfected partner. People who are s*xually active should correctly and consistently use condoms to reduce the risk of infection with syphilis and other STDs.
3. Why is having syphilis a problem during pregnancy?
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 conge***al 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 conge***al 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.
4. Where can I get tested?
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.
5. Should I tell my partner that I have syphilis?
Yes, you should tell your s*xual partner(s) that you have syphilis so they can get tested and treated
6. If I get treated, can I get syphilis again?
Yes. Even though treatment will cure your infection, you can get it again if you are exposed again.
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