Is a Rapid Plasma Reagin (RPR) Test?
A rapid plasma reagin (RPR) test is a blood test used to screen
you for syphilis. It works by detecting the antibodies that your body produces
to fight the infection.
Syphilis is a sexually transmitted infection (STI) that can
be fatal if left untreated. The RPR test allows your doctor to confirm the diagnosis
and start your treatment. This reduces the chances of complications and the
spread of the disease by an infected but unaware person.
Is an RPR Test Recommended?
Your doctor may order an RPR test for several reasons. It’s
a quick way to screen those at high risk for syphilis. Your doctor may also order
this test if you have syphilis-like sores or a rash. Doctors also routinely
screen pregnant women for syphilis using an RPR test.
states still require that people who are applying for a marriage
certificate get a screening test for syphilis. These states include
Mississippi, Montana, and the District of Columbia.
The RPR test measures antibodies to the disease rather than
the disease itself. It can also be used to check the progress of treatment for
syphilis. After a course of antibiotics, your doctor would expect to see the
number of antibodies drop and an RPR test could confirm this.
Is Blood for the RPR Test Obtained?
Doctors obtain blood for the RPR test with a simple blood test
called a venipuncture. This can be done in your doctor’s office or a lab. You
don’t need to fast or take any other special measures before this test. The
test involves the following steps:
- A healthcare provider will ask you to sit in a
comfortable chair or lie down on a cot or a gurney.
- They then tie rubber tubing around your upper
arm to help make your veins stand out. When they find your vein, they swab the
spot with rubbing alcohol to cleanse it and insert a needle into the vein. The
needle may produce a sudden, sharp pain, but it typically doesn’t last long.
- Once they have the blood sample, they’ll remove
the needle from your vein, hold pressure on the puncture site for a few
seconds, and offer you a bandage.
of the RPR Test
Venipuncture is minimally invasive and carries very few
risks. Some people complain of soreness, bleeding, or bruising after the test. You
can apply an ice pack to the puncture wound to help relieve these symptoms.
Some people may become light-headed or dizzy during the
test. Tell the healthcare provider if your dizziness lasts longer than a few
A normal blood sample shows no antibodies to syphilis.
However, your doctor cannot completely rule out syphilis if they see no
antibodies. Once you’ve been infected, it takes some time for your immune system
to create antibodies to fight the bacteria. Shortly after infection, a test may
not show any antibodies. This is known as a false negative.
False negatives tend to be more common in the initial and end
stages of infection. Among people who are in the second or middle stage of
infection, the RPR test results are nearly always accurate.
The RPR test also can produce false-positive results, suggesting you have syphilis when you
actually don’t. One reason for a false positive is the presence of another
disease that produces antibodies similar to the ones that fight syphilis. A few
of the conditions that can cause a false positive include:
- Lyme disease
- certain types of pneumonia, especially those
associated with a compromised immune system
Your doctor may ask you to wait a few weeks and then return
for another test if you show symptoms of syphilis but you have a negative RPR
test. This is because of the RPR test’s potential for a false negative.
Due to the risk of false-positive results, your doctor will
confirm the presence of syphilis with a second test before starting your
treatment. This test is called the fluorescent treponemal antibody-absorption
After the RPR Test
Your doctor will start you on a course of antibiotics,
usually penicillin, if your RPR and FTA-ABS test both show signs of syphilis.
New infections usually respond to treatment quickly.
At the end of treatment, the doctor will probably recommend
that you get another RPR test to make sure your antibody levels are dropping.