Lyme Disease Test

Results

A Lyme disease test detects antibodies to the Lyme disease bacteria Borrelia burgdorferi in the blood. The results of a Lyme disease test to detect antibodies (ELISA, IFA, Western blot) may be reported in titers. A titer is a measure of how much the sample can be diluted before the antibodies to the Lyme disease bacteria can no longer be detected.

A titer of 1 to 8 (1:8) means that antibodies can be detected when 1 part of the blood sample is diluted by up to 8 parts of a salt solution (saline). A larger second number means there are more antibodies in the blood. Therefore, a titer of 1 to 128 indicates more Lyme disease antibodies in the blood than a titer of 1 to 32.

Normal values may vary from lab to lab. Test results are usually available in 1 to 2 weeks.

Lyme disease test

Normal (negative):	No antibodies to Lyme disease bacteria are found. For the IFA test, the titer is less than 1:256.
	The polymerase chain reaction (PCR) test does not find any Lyme disease bacteria DNA.
Abnormal (positive):	Antibodies to Lyme disease bacteria are found. For the IFA test, the titer is equal to or greater than 1:256.
	The polymerase chain reaction (PCR) test detects Lyme disease bacteria DNA.

Normal (negative) values

A normal, or negative, test for Lyme disease can mean one of the following:

• You do not have Lyme disease. A negative PCR test usually means that you do not have a Lyme disease infection.
• You have Lyme disease but it does not show up on the test (false-negative). This is more likely with the antibody tests than with PCR. Reasons for a false-negative result include the following:
  • You have not yet made antibodies to the Lyme disease bacteria. The infection may be present, but it is too early to find antibodies. This is most likely to occur during the first several weeks of infection.
  • Blood levels of antibodies against Lyme disease bacteria are too low for the test to detect.
  • Occasionally, some people who were not treated correctly with antibiotics in the early stage of infection may not have antibodies to the Lyme disease bacteria in later stages of the illness.

Abnormal (positive) values

An abnormal, or positive, test for Lyme disease can mean one of the following:

• If antibodies are found, you may either have Lyme disease now or had the illness in the past.
• If Lyme disease bacteria DNA is found, you probably have an active Lyme disease infection. Once you have a Lyme disease infection, the DNA to the bacteria will usually stay in your body for the rest of your life.
• The result is a false-positive. Sometimes an antibody test for Lyme disease finds antibodies to other bacteria, such as syphilis, or viruses, such as the Epstein-Barr virus or the human immunodeficiency virus (HIV). The test may also find antibodies that develop as part of an immune response against the body's own tissues (autoimmune disease), such as rheumatoid arthritis or lupus. Your doctor may not be able to tell if the antibodies found in these tests are caused by a current Lyme disease infection.

The PCR test may be done to confirm an infection if you have a positive antibody test result.

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Author:	Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated: September 22, 2006
Medical Review:	Adam Husney, MD - Family Medicine Christine Hahn, MD - Epidemiology
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