syphilis test, RPR

syphilis test, RPR Rapid plasma reagin syphilis test, a blood test for syphilis that looks for an antibody that is present in the bloodstream when a patient has syphilis. A negative (nonreactive) RPR test is compatible with a person not having syphilis, but in the early stages of the disease, the RPR often gives false negative results. Conversely, a false positive RPR can be encountered in a patient with infectious mononucleosis, lupus, antiphospholipid syndrome, hepatitis A, leprosy, malaria, or, occasionally, pregnancy. See also syphilis; VDRL test.