• Syphilis is a sexually transmitted infection (STI) that if left untreated can lead to serious health problems.
• It is caused by bacteria called Treponema pallidum.
• Because it is caused by bacteria, syphilis can be cured with antibiotics.
• About half of people with syphilis have no symptoms or else their symptoms are very mild and similar to those from other health problems.
• You may be tested for syphilis as part of a routine check-up for STIs or else if you have symptoms that suggest you may have been infected.
• If you are pregnant, it is important that you are tested as syphilis can have a serious impact on your baby.

Syphilis is a sexually transmitted infection (STI) which means it spreads when you have vaginal, anal or oral sex with someone who has the infection. It can also be passed on from mother to baby during pregnancy. If left untreated, syphilis can lead to serious health problems. Cases of syphilis have more than doubled in the past 10 years, and the Australian Government has declared it a health priority.

Syphilis is classified in stages:

• Primary syphilis – when you are first infected you may have sores or ulcers around your genital area or mouth that can develop 10 to 90 days after you are infected and clear up within a few weeks. These are often painless and can go unnoticed.
• Secondary syphilis – your symptoms may include rashes, swollen lymph glands, fever, headaches or tiredness. These usually resolve by themselves, but if you don’t have any treatment you can be infectious for up to two or more years.
• Latent syphilis – this may develop if you go untreated. You have no symptoms, and you are not infectious, but the bacteria stay in your body for life, and you are at risk of developing tertiary syphilis.
• Tertiary syphilis – this develops in about one-third of people who have not been treated. In these cases, the infecting bacteria damage the brain, heart, blood vessels, liver, nerves, spinal cord, eyes, bones or joints. Symptoms can arise many years after your original infection and can lead to mental illness, blindness, other neurological problems, heart disease or death.

Pregnancy and congenital syphilis

Syphilis can cause severe complications in pregnancy and result in a premature baby, miscarriage or stillbirth. It can also be passed on to the baby as congenital syphilis. Sometimes, a baby is born without symptoms. Usually, symptoms develop in the baby in the first few weeks after infection, but sometimes they do not show up until months or even years later.

If you are pregnant, it is important that you are tested for syphilis at your first prenatal visit and, if you are at greater risk (such as if you live in an area where there is an outbreak of syphilis), throughout the pregnancy. You may also be tested at the time and soon after the birth of your baby. If you are pregnant, it is recommended you are at least tested at your first antenatal visit to prevent syphilis being passed on to your baby. If you live in an area where there is an ongoing syphilis outbreak, you should be tested at:

• the first antenatal visit
• 28 and 36 weeks
• the time of birth
• six weeks after the birth

If it is thought that a baby may have been born with congenital syphilis both mother and baby will be tested. The baby may be offered antibiotic treatment even if test results are negative. (See more in the “Your results” section below.)

Types of testing

Serology tests (indirect testing)

To find out if you have syphilis, you will first have blood tests that look for the antibodies your immune system makes to fight the bacteria. These types of tests are called serology tests. It can take a couple of weeks after you are infected before antibodies develop and you show a positive result.

All the available serology tests for syphilis have limitations and no single test can confirm a diagnosis by itself. Because of this, two types of antibodies are usually tested for:

• Treponemal antibody tests look for the antibodies your immune system makes specifically to fight the Treponema pallidum bacteria which causes syphilis. Your immune system protects you by making antibodies to attack substances that should not be in your body and could be harmful to you.
  Treponemal antibodies are detectable at about 10 to 90 days after you become infected and typically remain in your body for life. The tests most often used are CLIA (chemiluminescent immunoassay) and EIA (enzyme immunoassay) tests. The treponemal antibody test asks: has this person ever had syphilis?
• Non-treponemal antibody tests look for markers made when there is cell damage, and many infections can trigger them, including flu, HIV, EBV, measles, chickenpox, Covid-19 and pneumonia among others. Non-treponemal antibody testing shows if there is tissue damage due to an active infection. Non-treponemal antibodies are usually only found when you have an active infection and disappear over time whether you receive treatment or not. The most often used of these tests is RPR. The non-treponemal test asks: is there an active infection?

If either your treponemal or non-treponemal tests are positive, your sample can be used for further, more specialised tests that may be needed to make your diagnosis.

Your antibody test results together with the history you provide your doctor will help work out what stage of the disease you may be in and will help decide what treatment will be appropriate.

PCR tests (direct testing)

PCR is a test that looks directly for the genetic material (DNA) of the bacteria. It is an extremely accurate test that can be used together with treponemal and non-treponemal tests. PCR works best on samples taken directly from infected tissue, such as a swab from a syphilis ulcer. It is especially useful in early syphilis before antibodies are detectable. However, because syphilis sores are often painless, they can go unnoticed and the opportunity to test them is missed. If you have any symptoms at all that could be primary syphilis it is important to seek medical advice.

PCR is most helpful in diagnosing:

• Very early (primary) syphilis before antibodies appear
• Atypical or painless ulcers
• Congenital syphilis – babies who may have been born with syphilis
• To help clarify results if other blood tests are negative or unclear

PCR testing for syphilis is not limited to swabs from an ulcer, although this is the most common use. Sometimes other samples may be tested such as a vaginal swab or urine when the cause of an STI is unclear. PCR testing for syphilis in blood is not very accurate. This is because the bacteria circulates in the blood in very small numbers and there is not enough bacterial DNA for PCR to detect.

CSF testing
If you have tertiary syphilis that may have infected your brain or spinal cord (neurosyphilis), you may be asked to have a procedure to take a sample of the fluid from around your spinal cord called cerebrospinal fluid (CSF). This can be tested using PCR. This is only used if you have already received a positive treponemal antibody test result.

• Syphilis is a sexually transmitted infection which causes sores, a rash and can lead to more serious issues with internal organs.
• Syphilis is classified in stages: primary, secondary and tertiary
• Testing for syphilis can be quite complex and requires more than one type of testing.
  

Testing for syphilis can be requested by your doctor or clinic if you:

• have an ulcer or sore on your genitals or in your throat,
• are being treated for another sexually transmitted infection, such as gonorrhoea,
• are at special risk, such as being in close contact with a known case of infectious syphilis,
• are planning a pregnancy or as part of screening during pregnancy, because left untreated, syphilis can infect and cause severe illness to the developing baby, or
• have non-specific symptoms that suggest you could have syphilis.

Sample
Blood.

Swab or scraping of an ulcer.

CSF – fluid from around the spinal cord.

Any preparation?
None.

The results of treponemal and non-treponemal tests are given as negative or positive.

Testing for suspected primary syphilis, as part of a routine check up or pregnancy check up.

What testing to expect

• The first test you will have will be a treponemal antibody test.
• If you have ulcers or sores, a swab can be taken, and a PCR test can be done.
• Your doctors may take a swab at the same time to test for other bacterial and viral infections that cause ulcers and sores.
• They may also test for other STIs such as HIV and hepatitis B and C since it is common to be infected by more than one STI at the same time.

Negative results

• If the results of the tests are negative
• it is very unlikely that you have syphilis and your doctors may consider other causes of your symptoms.
• However, if you are in the early stages (the first two weeks after infection), you may need repeat testing to confirm the negative result. This is because treponemal antibody test results can be negative before antibodies have developed.

Positive results

• A positive treponemal test result means that you will have other tests to confirm the diagnosis.
  • RPR (a non-treponemal test) to gauge disease activity.
  • A second treponemal test using a different testing method from the first.
  • If the results of these tests are unclear, it is possible that the laboratory will do yet another (third) treponemal test as a final decision maker.
• A positive PCR test (done on an ulcer) means that you have a current infection. In the early stages of the disease, this test can be positive before antibodies are produced.

Testing for neurosyphilis (a syphilis infection in the brain)

What testing to expect

• Suspected neurosyphilis is first investigated with a treponemal test.
• Neurosyphilis is diagnosed by looking at your symptoms (memory loss, headaches, visual problems, stroke) and blood and CSF tests. There is no single test that can diagnose it on its own.

Negative results

• A negative treponemal result means that neurosyphilis is very unlikely.

Positive results

• If the treponemal blood test is positive, a PCR test may be used to confirm it. This is done on CSF.

Testing for congenital syphilis

What testing to expect

• If it is thought that a baby may have been born with congenital syphilis both mother and baby will be tested.
• Treponemal tests will be used for the mother and non-treponemal tests for the baby.
• Treponemal tests are not helpful in newborns because the baby will have the mother’s treponemal IgG antibodies whether it is infected with syphilis or not. This means the test will be positive even if the baby does not have syphilis.
• However, there is another test that looks for a special type of antibody called IgM antibodies. these antibodies cannot be passed to the baby by the mother—so if IgM antibodies are detected, it must have been produced by the baby. IgM antibody testing accuracy can be poor so this is used as a supportive test.

Negative results

• A negative non-treponemal test result does not definitely rule out syphilis, and the baby may be given antibiotic treatment

Positive results

• The baby’s antibody levels will be compared with the mother’s antibody levels and if the baby’s levels are much higher, then congenital syphilis is strongly suspected.
• If the baby’s antibodies are the same or lower than the mother, it is more likely that the antibodies are being transferred from the mother to the baby across the placenta.
• At birth, a baby may test positive even if it does not have syphilis. These maternal antibodies steadily disappear. They usually become undetectable by about 3–6 months, although sometimes they can be detectable for up to 12 months.
• Babies at risk of congenital syphilis may be tested repeatedly over six months.
• If the baby has syphilis, its immune system continues making antibodies. This means that antibody levels rise over time.
• A positive IgM result supports a diagnosis of congenital syphilis

Treatment

Syphilis is usually treated with the antibiotic penicillin, but other antibiotics can be used if you are allergic. New infections can be cured easily. A longer treatment is needed if you have been infected for more than two years or if it is unclear when you were infected. Follow-up blood testing is usually done after treatment to make sure the infection has resolved. Someone who has been previously treated can become re-infected with syphilis if they are exposed again.

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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