Obviously, a positive test for the bug itself would be the best and most direct method for diagnosing Lyme disease. These tests are known as PCR (polymerase chain reaction) tests. They identify the DNA of a bug in the blood stream.
However, Borrelia doesn’t like to live in the blood stream. Relying on a blood test to find the actual bug doesn’t make much sense. Borrelia prefers to live inside cells and tissues so it’s not very common to have a PCR blood test comes back positive for Lyme. A negative PCR test does NOT means a person is negative.
There is a newer PCR test available which looks for the presence of Borrelia in the urine. To avoid the same issues of the blood tests, the bug is coaxed or “provoked” out of hiding prior to collection. This is done through a variety of different methods such as vigorous exercise, Rolfing / deep tissue massage, and more recently using ultrasound.
The most common way of testing for bugs is looking for antibodies to the infections in the blood. These are the proteins our body makes in response to invaders. Antibodies bind to infections in an effort to destroy and facilitate their elimination.