An RPR Test is a blood test used to check for syphilis. Syphilis is a sexually transmitted disease caused by a bacteria called Treponema pallidum. It is typically passed from person to person through contact with a sore on the genitals or mouth. Syphilis can be tricky to diagnose as symptoms may not occur for a long time or it may present with a variety of symptoms that look like other diseases. Symptoms may include a single sore, a rash, fevers, fatigue, or hair loss.