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
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.