Syphilis is known as the "great imitator." This is because many of the symptoms of syphilis are the same as those seen in other diseases. In turn, laboratory tests are necessary to diagnose syphilis.
There are two ways to diagnose syphilis. If you have a sore (primary syphilis) or pox-like lesions (secondary syphilis), your doctor can collect a small sample and send it to a lab for examination under a microscope. Your doctor can also collect a sample of blood and send it to a lab for analysis. During the first two to three weeks of infection, there is a possibility of a blood test coming back negative when in fact you are positive (a false-negative result). Another test, using the same sample of blood, can be done to confirm whether or not the bacterium is present.