This type of blood testing is used the most when trying to make a diagnosis of Lyme disease. While blood testing is most common, joint or spinal fluid can and may also be tested. It may take as long as two months after becoming infected for antibodies to show up. However, once they are formed they can remain in the body for many years, even after the infection has been successfully treated. Finding the antibodies will not tell the doctor whether the patient's infection was recent or happened a while ago. There are three different antibody tests used in trying to make a diagnosis of Lyme disease:
• The enzyme-linked immunosorbent assay, or ELISA, is a fast and common test that can be done to identify the antibodies. It is also the most sensitive screening test for this infection.
• The indirect fluorescent antibody (IFA) is a blood test that can also be used to screen for the associated antibodies.
• The Western blot test identifies the antibodies and is often done to confirm or deny the results of the ELISA or IFA blood tests. When chronic Lyme disease is suspected, this is the blood test most often used.
Antibody testing will typically be done in two steps. It will use either the IFA or ELISA and then the Western blot test to confirm the results. ELISA is used more often than IFA because it is deemed more accurate and reliable, but if ELISA is unavailable, IFA is done. Everyone who has a borderline positive or positive ELISA or IFA should have the Western blot test done.