Test Overview

Syphilis tests tell if a person has this disease. 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. That means it is spread through sexual contact: vaginal, anal, or oral sex.

Testing is done on blood, body fluid, or tissue samples.

If a first screening test shows signs of syphilis, another test is done to confirm a syphilis infection.

Screening tests

Tests used to screen for syphilis include:

  • Venereal disease research laboratory (VDRL) test. 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.
  • Rapid plasma reagin (RPR) test. The RPR test also finds syphilis antibodies.

Tests to confirm syphilis

Tests used to confirm a syphilis infection include:

  • Enzyme immunoassay (EIA) test. This blood test checks for syphilis antibodies. A positive EIA test should be confirmed with either the VDRL or RPR tests.
  • Fluorescent treponemal antibody absorption (FTA-ABS) test. This test also checks for antibodies. It can be used to find syphilis except during the first 3 to 4 weeks after exposure. The test can be done on a sample of blood or spinal fluid.
  • Treponema pallidum particle agglutination assay (TPPA). This test also checks for antibodies. It is used after another method tests positive for syphilis. This test is not done on spinal fluid.
  • Darkfield microscopy. This test uses a special microscope to look for the syphilis germ in a sample of fluid or tissue from an open sore. This test is used mainly to diagnose syphilis in an early stage.
  • Microhemagglutination assay (MHA-TP). The MHA-TP is used to confirm a syphilis infection after another test shows positive results for syphilis.

Why It Is Done

A syphilis infection can spread through the bloodstream to all parts of the body. If not treated, syphilis can cause severe heart disease, brain damage, spinal cord damage, blindness, and death.

A test for syphilis is done to:

  • 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 Centers for Disease Control and Prevention (CDC) and the U.S. Preventive Services Task Force (USPSTF) recommend that all pregnant women be screened for syphilis early in pregnancy.1, 2
  • Confirm that a person has syphilis.

Screening for syphilis and other sexually transmitted infections is often done for people who engage in sexual behaviors 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 or medicine used to numb the skin (anesthetics).
  • Have had bleeding problems or take blood-thinners, such as aspirin or warfarin (Coumadin).
  • 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 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 (What is a PDF document?).

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

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 testing.

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. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

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 a 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.

Bleeding can be a problem for people who have bleeding disorders or who take blood-thinning medicines such as aspirin or warfarin (Coumadin). If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

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 disease. 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.

Darkfield microscopic examination
Normal:

No syphilis germs are seen.

Abnormal:

Syphilis germs are seen.

 

Syphilis tests of blood and spinal fluid
Normal:

No syphilis antibodies are found. This is called a nonreactive 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 inconclusive or equivocal.

 

Venereal disease research laboratory (VDRL) and rapid plasma reagin (RPR) tests
Normal:

Syphilis antibodies are not found. This is called a nonreactive or negative result.

Abnormal:

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

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

You may not be able to have the test, or the results may not be helpful, 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.

What To Think About

Test results

  • A reactive or positive test result does not always mean that you have syphilis. Other conditions can cause positive test results. These include injecting illegal drugs, recent vaccinations, endocarditis, autoimmune diseases (such as systemic lupus erythematosus, or SLE), tuberculosis, mononucleosis, leprosy, malaria, hepatitis, Lyme disease, rheumatoid arthritis, and, in rare cases, pregnancy.
  • With treatment, a positive VDRL or RPR test result usually becomes negative. Positive FTA-ABS, MHA-TP, or TPPA tests stay positive for a lifetime, even after syphilis has been cured.
  • In the United States, your health professional must report to the state health department that you have syphilis.

Syphilis and HIV infection

  • Sores caused by syphilis make it easier to get and spread an HIV infection.
  • People with HIV who have a negative VDRL test should have a second test for syphilis if the infection is suspected.

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

References

Citations

  1. Centers for Disease Control and Prevention (2010). Syphilis section of Sexually transmitted diseases treatment guidelines, 2010. MMWR, 59(RR-12): 26–39. Also available online: http://www.cdc.gov/std/treatment/2010/default.htm.
  2. U.S. Preventive Services Task Force (2009). Screening for syphilis infection in pregnancy: U.S. Preventive Services Task Force reaffirmation recommendation statement. Annals of Internal Medicine, 150(10): 705–709.

Other Works Consulted

  • Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Credits

ByHealthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer Kirtly Jones, MD - Obstetrics and Gynecology

Current as ofNovember 14, 2014