Diagnosis

Many signs and symptoms of Lyme disease are often found in other conditions, so diagnosis can be difficult. What's more, ticks that transmit Lyme disease can also spread other diseases.

If you don't have the characteristic Lyme disease rash, your doctor might ask about your medical history, including whether you've been outdoors in the summer where Lyme disease is common, and do a physical exam.

Lab tests to identify antibodies to the bacteria can help confirm or rule out the diagnosis. These tests are most reliable a few weeks after an infection, after your body has had time to develop antibodies. They include:

• Enzyme-linked immunosorbent assay (ELISA) test. The test used most often to detect Lyme disease, ELISA detects antibodies to B. burgdorferi. But because it can sometimes provide false-positive results, it's not used as the sole basis for diagnosis.

  This test might not be positive during the early stage of Lyme disease, but the rash is distinctive enough to make the diagnosis without further testing in people who live in areas infested with ticks that transmit Lyme disease.

• Western blot test. If the ELISA test is positive, this test is usually done to confirm the diagnosis. In this two-step approach, the Western blot detects antibodies to several proteins of B. burgdorferi.