IgM antibodies are usually made by your body when the infection is new and recent, while IgG antibodies are usually made some weeks later. The Western blot test looks at whether you have an immune response - the production of IgM or IgG antibodies - to specific proteins (antigens) on the Lyme disease bacteria. So, if your ELISA test is negative, you may want to ask your doctor to repeat the test in two to four weeks, or to get another sample of your blood for testing a week or so later. Because the first test may not pick up antibodies soon after possible exposure to Lyme disease, that means a person with Lyme may never get the second test. The CDC testing guidelines recommend a second test only if the first test is positive or unclear. A possible drawback of the two-step testing system You should not need to go back to the lab. These tests can be run on the blood sample used for the first test. Because these tests are newer, not all doctors have experience with them and not all labs have access to them. The other option is to do a second ELISA test, which measures antibodies to a specific protein found on Lyme disease bacteria. The Western blot test has been part of the two-step testing system since 1994 and is more commonly used. One is called a Western blot, which looks at how your antibodies react to specific parts of the Lyme disease bacteria. There are two options for the second test. The second test: Western Blot or a second ELISA

Because it can take some time for your body to produce antibodies, this test isn’t always accurate soon after a person is infected. This blood test is for antibodies against the Lyme disease bacteria. The first test: ELISA (enzyme-linked immunosorbent assay) Using today’s tests it is difficult to distinguish between current and previous infections, so if you were previously diagnosed with Lyme disease and may have been re-infected, your doctor should make the diagnosis based on your symptoms and risk factors. In some cases, a Lyme test may not be helpful. If you think you may have Lyme disease, but your doctor hasn’t considered it or has ruled it out before testing you for it, here’s how you can start a conversation: Give your doctor a list of Lyme disease symptoms and risk factors, and ask them if, given your own symptoms and risk factors, Lyme disease could be a possible cause and whether you should be tested. If you have been traveling, your doctor might test you for species of Borrelia that cause Lyme disease in other parts of the world. Your doctor may also do tests to see if other conditions with similar or overlapping symptoms - for example, thyroid disease, autoimmune disease, or other tick-borne diseases - could be causing your symptoms. Laboratory tests can support a clinical diagnosis, but should not be used on their own to confirm or rule out a current Lyme disease diagnosis. Your doctor will consider whether your symptoms and risk factors suggest Lyme disease when deciding whether you need a Lyme test.

By that time, Lyme disease is harder to treat, and long-term complications are more likely, so an early, accurate diagnosis is very important. That’s why Lyme disease cases may be missed, and as many as 40% of Lyme disease cases are not diagnosed until a later stage of the disease. Using today’s tests, it is difficult to distinguish between an old Lyme disease infection and a new one. This may result in Lyme diagnoses being missed because symptoms are attributed to another illness. Symptoms of Lyme disease like fever and body aches can also be caused by other illnesses. It is also possible that a person may not notice a rash before it goes away. But up to 30% of people who get Lyme disease never get a rash. The only sure sign of Lyme disease is an erythema migrans (EM) rash, which often has a bullseye shape. That’s because Lyme tests look for proteins created by your immune system to help you fight off infection (antibodies), rather than for the infection itself, and it can take a few weeks for your body to make enough antibodies to cause a positive test. Tests are less accurate for a short period of time after you first become infected. There are several reasons it can be hard to diagnose Lyme disease.

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