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RPR (rapid plasma reagin) Test

A rapid plasma reagin (RPR) test is a blood test used to screen you for syphilis. It works by detecting the nonspecific antibodies that your body produces while fighting the infection.

Syphilis is a sexually transmitted infection (STI) caused by the spirochete bacterium Treponema pallidum. It can be fatal if left untreated.

Combined with specific antibody testing, the RPR test allows your doctor to confirm the diagnosis of active infection and start your treatment. This reduces the chances of complications and the spread of the disease by an infected but unaware person.

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 used to require that people who are applying for a marriage certificate get a screening test for syphilis. The only state that still requires a blood test of any type is Montana, and a syphilis test is no longer included.

The RPR test measures antibodies that are present in the blood of someone who has syphilis, rather than the bacterium that causes the disease. It can also be used to check the progress of treatment for active syphilis. After a course of effective antibiotic therapy, your doctor would expect to see the number of antibodies drop, and an RPR test could confirm this.