Syphilis tests detect
antibodies to the bacterium that causes
syphilis (Treponema pallidum)
in blood, body fluid, or tissue. The tests are used to screen for or to confirm
a syphilis infection.
Syphilis is a
sexually transmitted infection (STI) that is usually
spread during sexual contact, including kissing 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
- Enzyme immunoassay (EIA) test. This is a newer blood test that checks for antibodies to the
bacteria that cause syphilis. A positive EIA test should be confirmed with
either the VDRL or RPR tests.
Tests used to diagnose syphilis include:
- 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 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.
- Some states require the VDRL screening test
before a couple can obtain a marriage license.
- 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
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.