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Syphilis Tests

Test Overview

Syphilis tests tell if a person has this infection, or if they've had an infection in the past. They look for antibodies to the bacterium, or germ, that causes syphilis. Some tests look for the syphilis germ itself.

Syphilis is a sexually transmitted infection (STI). That means it is spread through sexual contact: vaginal, anal, or oral sex, or sometimes just close physical contact, like foreplay. If you're pregnant and you have syphilis, you can pass the infection to your baby.

These tests are usually blood tests. Depending on your symptoms, you may have more tests done on body fluids or tissue samples.

If a first screening test is positive, the lab will run two more tests to be sure you have a syphilis infection. It can take up to 12 weeks from the time you're exposed to syphilis for blood tests to show the infection.

Syphilis tests done in Alberta

  • Serological test for syphilis enzyme immunoassay (STS-EIA). This is the first screening blood test. It tests for syphilis antibodies. If it is positive, this could mean that you've had syphilis in the past, or that you have it now. It could also be a false positive. The sample will be sent for two more tests, including one to confirm the positive result. If you've tested positive for syphilis in the past, this test will likely be positive for life.
  • Treponema pallidum particle agglutination assay (TPPA). This test checks for syphilis antibodies. It is used after another method tests positive for syphilis. If you've tested positive for syphilis in the past, this test will likely be positive for life.
  • Rapid plasma regain (RPR). You'll have this blood test if the first blood test (STS-EIA) test is positive. This test is used to find out how far along the infection is (stage of infection), to see how you're responding to treatment, and to find out if you've been infected again.
  • Polymerase chain reaction (PCR) test. This can detect syphilis DNA from a swab of a sore (skin lesion) if you've been recently infected.
  • Venereal disease research laboratory (VDRL) test. This test may be done after a positive syphilis blood test, if your doctor thinks the infection may have spread to the nervous system ( neurosyphilis). The VDRL test checks blood or spinal fluid for an antibody that can be produced in people who have syphilis. This antibody is not produced as a reaction to syphilis specifically, so the test result could be abnormal for reasons other than syphilis.
  • Fluorescent treponemal antibody absorption (FTA-ABS) test. This test may be done after a positive syphilis blood test, if your doctor thinks the infection may have spread to the nervous system ( neurosyphilis). It also checks for antibodies. This test only works starting at around 4 weeks after you've been exposed to syphilis. It can be done on a sample of blood or spinal fluid.

Why It Is Done

A syphilis infection can spread through your bloodstream to all parts of your body. Without treatment, syphilis can cause severe heart disease, brain damage, spinal cord damage, blindness, and death. If you're pregnant, your baby could develop congenital syphilis, and other health problems. There is also a risk of your baby dying before they are born (stillbirth).

A test for syphilis is done to:

  • Confirm that a person has syphilis.
  • Screen for syphilis or check how well treatment is working. Screening tests help your doctor look for a certain disease or condition before any symptoms appear. This increases the chance of finding the infection when it can be cured or treated to avoid long-term problems.
    • The Public Health Agency of Canada recommends that anyone who is pregnant be screened for syphilis early in pregnancy.

Screening for syphilis and other sexually transmitted infections is often done for people who engage in sexual behaviours that put them at risk. If you have syphilis, your sex partner or partners should be told, tested, and treated to prevent serious problems and to stop the spread of the disease.

How To Prepare

Tell your doctor if you:

  • Are taking any medicines, such as antibiotics.
  • Are allergic to any medicines, especially antibiotics.
  • Take a blood thinner, or if you have had bleeding problems.
  • Are or might be pregnant.

If you have syphilis, do not have sex until the test results show that you are no longer infected or until you and your sex partner or partners have completed treatment and the infection has been cured. Your sex partners should be tested and treated as well.

If you think you might have syphilis, do not have sex until testing shows that you are not infected.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form .

How It Is Done

A syphilis test may be done on a sample of blood, sore, skin, or spinal fluid, depending on which type of test is done.

Blood sample

Blood test from a vein

The health professional taking a sample of your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.

Sore or skin sample

A sample of fluid or tissue may be taken from an open sore or from a rash that might be caused by syphilis.

  • A fluid sample is obtained by gently pressing the sore.
  • Skin or mucous membrane samples may be obtained by gently rubbing a cotton-tipped swab over the area.

Spinal fluid sample

A spinal tap (lumbar puncture) is done to collect a spinal fluid sample for syphilis when the infection may have spread to the nervous system ( neurosyphilis).

For a lumbar puncture, a thin needle is inserted into the spinal canal in the lower back. After the needle is in place, a small amount of fluid is removed from the spinal canal. To learn more, see the topic Lumbar Puncture.

How It Feels

Blood sample

The blood sample is taken from a vein in your arm. You may feel nothing at all from the needle, or you may feel a quick sting or pinch. When blood is taken from a vein, an elastic band is wrapped around your upper arm and may feel tight.

Sore or skin sample

You may feel some discomfort when fluid is collected from an open sore. But syphilis sores usually are not very tender or painful.

Spinal fluid sample

You may feel some discomfort during a lumbar puncture to collect spinal fluid. To learn more, see the topic Lumbar Puncture.

Risks

Blood sample

There is very little chance of a problem from having a blood sample taken from your vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.

Sore or skin sample

There is very little risk of problems from having a sample taken from an open sore, skin rash, or mucous membrane.

Spinal fluid sample

There is little risk linked with having a lumbar puncture to obtain a spinal fluid sample. To learn more, see the topic Lumbar Puncture.

Results

Syphilis tests tell if a person has the infection. They look for antibodies to the bacterium, or germ, that causes syphilis. Some tests look for the syphilis germ itself.

Results are usually available in 7 to 10 days.

Syphilis tests of blood and spinal fluid

Normal:

No syphilis antibodies are found. This is called a non-reactive or negative result.

Abnormal:

Antibodies are found. This is called a reactive or positive test.

A result that is not clearly normal or abnormal is called indeterminate.

If you've tested positive for syphilis in the past, two of the tests that look for antibodies will likely be positive for life (EIA and TPPA). The RPR test is used to tell if you've been cured. It's also used to tell if you have been infected again and need to be treated again.

The accuracy of testing often depends on the stage of syphilis. Testing may need to be repeated if:

  • Results of the first test are uncertain.
  • You have had repeated exposure to syphilis, such as from repeated unprotected intercourse.

What Affects the Test

A test for syphilis is based on your risk of infection. You can, and should, still be tested even if:

  • You use antibiotics before you have the test.
  • You have a blood transfusion in the weeks before having the test.
  • You have another condition or disease, such as lupus, liver disease, HIV infection, or a tropical bacterial infection called yaws.
    • It's common to have HIV and syphilis infections at the same time. If you have HIV, you should still get tested for syphilis if you are at risk. Talk about it with your healthcare provider.
    • A history of yaws or pinta infection (long-term infections of the skin, bone, and cartilage, a lot like the syphilis germ) does affect the test. It is difficult for the tests to determine the difference between these infections, so you would be offered syphilis treatment if your test is positive.

What To Think About

Test results

  • In Canada, syphilis is a notifiable infection. This means that healthcare providers need to report it to Public Health. This allows for your sexual partners to get tested and treated for syphilis. It helps to stop the infection from spreading and will also help stop you from getting infected again. Learn more about reporting STIs and your privacy.

Syphilis and HIV infection

    Sores caused by syphilis make it easier to get and spread an HIV infection.

To learn more about testing for sexually transmitted infections, see:

References

Citations

  1. Public Health Agency of Canada (2013). Canadian guidelines on sexually transmitted infections: Specific population—Pregnancy. Public Health Agency of Canada. http://www.phac-aspc.gc.ca/std-mts/sti-its/cgsti-ldcits/section-6-4-eng.php. Accessed October 3, 2014.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
  • Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.

Credits

Adaptation Date: 3/8/2021

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services

Adapted with permission from copyrighted materials from Healthwise, Incorporated (Healthwise). This information does not replace the advice of a doctor. Healthwise disclaims any warranty and is not responsible or liable for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.