The two most common diagnostic tests for Lyme are the enzyme-linked immunosorbent assay (ELISA) and the Western blot. Both of these blood tests measure the presence of antibodies that form in your body if you are infected with Borrelia burgdorferi, the bacterium that causes Lyme. This marker is part of the ELISA assay.
ELISA – This is the screening test used when Lyme disease is first suspected. It measures the levels of antibodies against Lyme bacteria. According to the Centers of Disease Control and Prevention, if the test proves negative for the antibodies, no further test is recommended. If the ELISA is positive or unclear, a second test is recommended to confirm the disease. However, the ELISA is falsely negative nearly 50% of the time. Sadly, many people are never tested beyond this point and are told they do not have Lyme disease when in fact they may be infected.
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.
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.
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