Screening for Lyme Disease

Antibodies are the body’s defense against an infection. If you have been infected with the Lyme disease bacteria, your body will make specific antibodies to fight it. It takes about four weeks or more for these antibodies to become detectable. Examples include:

• Antibody titer (ELISA or IFA)—This test measures the level of Lyme disease antibodies in the blood.
• Western blot—This test detects the presence of specific antibodies to Lyme disease in the blood and supports the ELISA test results

Both of these tests can have false negative results (the test is negative even though you are infected) or false positive results (the test is positive even though you are not infected).

Reasons why false negatives may occur include:

• The test is performed too soon after infection.
• Too few or no antibodies are made.
• The test is performed incorrectly.

Reasons why false positives may occur include:

• The test is performed incorrectly.
• Your immune system produces unrelated antibodies, which appear on the test as if they were produced in response to Lyme disease.

These tests look directly for the bacteria, or pieces of it, in the blood and other fluids of the body, such as urine and spinal fluid. Two main types are:

• Antigen detection tests—These look for a unique protein from the Lyme disease bacteria that may be in body fluids. This test is useful for detecting Lyme disease in certain situations, such as:
  • If you are taking antibiotics
  • During a later flare-up of symptoms
• Polymerase Chain Reaction (PCR)—This test can multiply the number of pieces of the bacteria in the test fluid, making it easier to detect.