Rapid Plasma Reagin
Does this test have other names?
RPR test, syphilis test
What is this test?
The rapid plasma reagin (RPR) test is a blood test that looks for antibodies to syphilis.
Syphilis is a sexually transmitted infection (STI) that first causes symptoms seen
with many other illnesses. Early symptoms include rash, fever, swollen glands, muscle
aches, and sore throat.
In addition, people who have early-stage syphilis may have sores (lesions). These
sores can pass the infection on to other people during sexual contact.
If not detected, syphilis can stay in the body for years causing harm to internal
organs. Over time it can cause numbness, paralysis, blindness, and even death. But
it can be easily cured if treated in the early stages. Treatment involves receiving
one or more shots of a form of penicillin (penicillin G benzathine).
The RPR test looks for antibodies that react to syphilis in the blood. This means
the test doesn't detect the actual bacteria that cause syphilis. Instead, it looks
for antibodies against substances given off by cells that have been harmed by the
Why do I need this test?
You may need this test if you have ever been sexually active and show signs of syphilis.
These signs may include:
Small, painless sores (chancres) at the place where syphilis invaded your body
Skin rash. Sometimes this is on the palms of your hands or the bottoms of your feet.
Swollen lymph glands
Years after infection, symptoms in the final stages of the disease include numbness,
paralysis, blindness, and dementia or death.
The RPR test is often used to check treatment of a syphilis infection. If you are
being treated for syphilis, you need to stop having sex until your sores have fully
healed. Your partner(s) should also be told so they can also be tested and treated
If you are a sexually active adult with HIV/AIDS, you may need the RPR test at least
once a year. Screenings for syphilis and other STIs are also recommended every 3 to
6 months if you have had unprotected sex, multiple sex partners, or intercourse while
under the influence of illegal drugs. It's routine to be tested for syphilis and other
STIs during pregnancy. Condoms can help prevent the spread of syphilis. But they don't
protect against sores outside the condom area.
You may also need the RPR test if you are in a group that is at high risk for syphilis.
This includes sex workers, men who have sex with men, or adult prisoners. Syphilis
can infect or even possibly kill a developing baby, so it's very important that all
pregnant women be screened with an RPR. If it's positive, the woman can get treatment
to lower the chance of passing the disease to the fetus.
What other tests might I have along with this test?
RPR is not specific to just syphilis. If your RPR test is positive, you will need
more tests to confirm that you have syphilis. One of the most common tests used to
confirm a syphilis diagnosis is the T. pallidum enzyme immunoassay. Other tests may
Fluorescent treponemal antibody absorption
Microhemagglutination test for antibodies to T. pallidum
T. pallidum particle agglutination assay
Tests for other STIs
These tests will generally rule out a false-positive result. This means your test
is positive even if you don't have syphilis. Your healthcare provider may also be
able to detect the syphilis bacteria by taking a sample from a moist sore and looking
at it under a microscope.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
A negative or nonreactive result means you don't likely have syphilis. Positive results
are given as a ratio in titers. This tells your healthcare provider the amount of
antibodies in your blood.
Here are some general results:
If you have a history of syphilis and your RPR test is negative or nonreactive, it's
likely that you no longer have syphilis.
A positive RPR test should be followed by another type of test to diagnose syphilis.
If you have been treated for syphilis in the past, an RPR test that shows a titer
increase of fourfold means you likely have a new syphilis infection if you were not
fully treated in the past.
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Taking a blood sample with a needle carries risks. These include bleeding, infection,
bruising, or feeling lightheaded. When the needle pricks your arm, you may feel a
slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Your test results may be false-positive for many reasons. These include pregnancy,
IV drug use, tuberculosis, chronic liver disease, recent vaccines, or inflammation
of the heart lining or valves (endocarditis). You may also have a false-positive result
if you have one of a number of infections. These include rickettsial infections such
as typhus or Rocky Mountain spotted fever.
Your results may be false-negative if the test is done too soon after you are infected
with syphilis. It takes 14 to 21 days after infection with the spirochetes for your
body's immune response to be found by the test. Drinking alcohol within 24 hours of
the test also can give a false-negative result.
How do I get ready for this test?
Follow your healthcare provider's instructions for getting ready for the test. You
may need to not eat or drink anything but water for about 8 hours before the test.
Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements
you are taking. This includes medicines that don't need a prescription and any illegal
drugs you may use.