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Syphilis Tests

Syphilis tests detect antibodies to the bacterium that causes syphilis (Treponema pallidum) in blood, body fluid, or tissue. If an initial screening test shows signs of syphilis, another test is done to confirm a syphilis infection.

Syphilis is a sexually transmitted infection (STI) that is usually spread through vaginal, anal, or oral sex.

Tests used to screen for syphilis include:

  • Venereal disease research laboratory (VDRL) test. The VDRL test checks for an antibody that can be produced in people who have syphilis. This antibody is not produced as a reaction to the syphilis bacteria specifically, so this test is sometimes not accurate. The VDRL test may be done on a sample of blood or spinal fluid. The VDRL test is not very useful for detecting syphilis in very early or advanced stages.
  • Rapid plasma reagin (RPR) test. The RPR test also detects syphilis antibodies.

Tests used to diagnose syphilis include:

  • Enzyme immunoassay (EIA) test. This blood test checks for antibodies to the bacteria that cause syphilis. A positive EIA test should be confirmed with either the VDRL or RPR tests.
  • Fluorescent treponemal antibody absorption (FTA-ABS) test. The FTA-ABS test checks for antibodies to the bacteria that cause syphilis and can be used to detect syphilis except during the first 3 to 4 weeks after exposure to syphilis bacteria. The test can be done on a sample of blood or spinal fluid.
  • Treponema pallidum particle agglutination assay (TPPA). The TPPA test is used to confirm a syphilis infection after another method tests positive for the syphilis bacteria. This test detects antibodies to the bacteria that cause syphilis. This test is not done on spinal fluid.
  • Darkfield microscopy. This test uses a special microscope to examine a sample of fluid or tissue from an open sore (chancre) for the syphilis bacteria. 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 method tests positive for the syphilis bacteria.

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 treatment for a syphilis infection. 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 syphilis infection is present.

Screening for syphilis and other sexually transmitted infections (STIs) 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 notified, tested, and treated to prevent serious complications and to stop the spread of the disease.

WebMD Medical Reference from Healthwise

Last Updated: October 08, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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