To see whether a person has syphilis caused by a bacteria called Treponema pallidum, and how far the disease has progressed. This information helps the doctors to choose the best possible treatment. Timely diagnosis of the infection also helps to cure the disease early and decrease the chances of complications.
Blood - Most common method used for testing is doing a blood test by taking blood from your vein. Your body produces antibodies (a type of protein) when infected with syphilis. This antibody can be tested and measured in your blood to diagnose syphilis.
Swab/scrape – If you have a sore/ulcer then a swab can be taken from that to test under the microscope for the bacteria (less commonly done nowadays) or it can be tested for bacterial genetic material (PCR, polymerase chain reaction)
CSF - In certain cases, if syphilis involves the brain, doctors can put a needle through your back to tap some fluid (CSF, Cerebrospinal fluid), which can be tested for infection.
The test is looking for evidence of Treponema pallidum, the bacterium that causes syphilis. Syphilis is a sexually transmitted disease. It is easily treatable but can cause severe health problems if left untreated.
The evidence of the presence of bacteria are:
If syphilis producing bacteria enters your body then the body’s defence system (immune system) would start producing proteins against the invading bacteria to try to fight the infection. These proteins are called antibodies. In laboratories these antibodies, which are produced in response to syphilis infection can be identified and measured by tests called serological tests. Doctors can interpret this test result to find out if you are infected and if infected, how far the infection might have progressed. Doctors might need to repeat the test to confirm the diagnosis and interpret the result better.
If you have a sore, a swab or scrape may be collected to look for the bacteria under the microscope. It is called dark ground microscopy. This test is infrequently done now as it needs a lot of expertise and antibody testing is easier to do, quicker and reliable.
Bacterial genetic material
This test is called PCR (polymerase chain reaction). It looks for Treponema pallidum genetic material in a sample directly taken from the sore/ulcer. This test is only available in a few specialised (reference) laboratories in the UK.
How is the sample collected for testing?
Usually the samples are collected in a genitourinary medicine (GUM) clinic, Sexual health clinic or in a GP surgery. However it is possible for the test to be done in hospitals as well.
There are several different methods and tests for the identification of syphilis infection. A sample may be:
- A scraping from a sore on the affected area (the cervix, penis, anus, or throat)
- A blood sample from a vein in your arm to detect antibodies to syphilis in your blood
- A spinal tap (lumbar puncture) may be necessary if you have late or latent stages of the disease to check for infection of the nervous system. This involves passing a needle into the back to obtain some fluid.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
The test is done to diagnose syphilis or to monitor the response to the treatment.
Syphilis infection evolves through different stages.
Stages Clinical development Laboratory test Primary syphilis It is marked by development of a painless sore/ulcer called chancre at the site where the bacteria enter the body. It develops approximately 3 weeks (could be longer) after bacteria entering the body. It disappears even without treatment but the disease persists unless treated The bacteria can be found in these lesions and by taking a scrape they can be seen under the microscope. However it needs an expert to do the test. This material can be examined for bacterial genetic material by a method called PCR. This test is only available in a few specialised laboratories in the UK.
Antibody generated against bacteria can be measured as well but some antibodies may take time to develop. Some of the test may not be positive in this stage and may need repeating
Secondary syphilis If untreated the bacteria enters the bloodstream and many other parts of the body. It may take 2 to 12 weeks’ time from the appearance of the sore. The body tries to fight the bacteria by producing proteins called antibodies and with specialised cells. In this stage identifying and measuring the protein helps with diagnosis (Serology). Serology is widely used nowadays. There are 2 types of serology tests available. One type of test looks for proteins which are generated in response to syphilis infection but may not be directed against the bacteria itself. These are called non treponemal tests. By nature these tests are very sensitive but can also give false positive results in a small group of people. These types of protein (antibody) gradually disappear with treatment; hence these antibodies can be measured to check if the treatment is successful.
A second group of serology tests looks for proteins which are specifically directed against Treponema pallidum, the bacteria. These tests are not as sensitive as the 1st group but the chance of false positive are low.
Latent syphilis In latent syphilis the disease progresses silently without any symptoms or signs. This stage can last from years to decades. The presence of the disease can be found by serology tests. Late syphilis It can develop 5-30 years after the infection if not treated with antibiotics. It usually involves the brain, heart, blood vessels, bones, skin etc. Diagnosis is done by serology.
In the UK, typically a blood sample is tested using one sensitive test, if positive, more test are performed to determine the stage of infection. A test may be negative in very early stages of infection and should therefore be repeated, if necessary. This will be guided by your doctor.
When is it requested?
A doctor may request the test:
- If you have symptoms, such as a chancre (ulcer or sore) on the genitals or throat;
- If you are being treated for another sexually transmitted disease, such as gonorrhoea;
- If you are pregnant, because untreated syphilis can infect and even kill a developing fetus; or
- If you complain of non-specific symptoms that resemble those of syphilis, to determine the exact cause of your illness.
- If your partner has been diagnosed with syphilis.
What does the test result mean?
Test Sample Comments Disadvantages Serology Blood/ CSF is tested for antibodies. Not specific for the bacteria itself but the level increases in syphilis.
The level goes down with treatment - useful in monitoring the treatment
False positive results may be seen in - IV drug abuse, pregnancy, Lyme disease, Lupus, tuberculosis etc.
False negative results may be seen in secondary and latent syphilis, especially in someone with HIV.
Blood Some specific tests become positive usually within 2 weeks of bacteria entering the body (EIA IgM)
Specific tests are usually always positive by the time secondary/latent syphilis starts or even earlier.
Direct detection of bacteria/dark ground microscopy Scraping of the sore tested under microscope Can diagnose syphilis if bacteria seen, useful in primary stage. Nor reliable from sore(s)in the anal or oral area.
Test may need repeating
PCR Scraping (and occasionally tissue, CSF) tested for bacterial genetic material. Can diagnose syphilis if positive. Sensitive and specific. Not readily available.
In the UK usually a panel of serology tests are done in the laboratory. The Laboratory may use a very sensitive test to screen first to ensure that they do not miss any syphilis cases. Then they follow up positive test results with other tests before making the result available to the doctors. For all the new positive cases usually a repeat blood sample is request to confirm the result.
Is there anything else I should know?
Some syphilis tests are not highly-specific and may give a falsely positive result. This is to reduce the risk of missing an infection. Positive tests are retested with additional more specific test to reduce the chance of a false positive result.
If you are sexually active, you should consult your doctor about any suspicious rash or sore in the genital area.
If you are infected, your sexual partner(s) must get tested and treated. A Genitourinary Medicine (GUM) clinic can give you help in doing this.
What are the symptoms of syphilis?
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, called a chancre, appears, usually on the part of the body exposed to your partner’s ulcer, such as the penis or vagina. The chancre may be painless and go unnoticed, and it disappears within a few weeks.
What will happen if I don't get treated?
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 all cases will progress 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.
How is syphilis transmitted?
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 mother can spread the disease to her fetus, with serious and potentially fatal consequences for the baby.
How is it treated?
How can syphilis be prevented?