Test Overview
A Lyme disease blood test detects
antibodies to the
Lyme disease
bacteria Borrelia burgdorferi. It is spread by certain
kinds of ticks.
Lyme disease may be difficult to diagnose because its symptoms are similar to
those of many other illnesses. If Lyme disease is suspected, a careful medical
history and physical examination will be done. Antibody tests can
sometimes be used to help confirm a diagnosis of Lyme disease. Other
tests may be done in certain situations.
Antibody Tests
Antibody tests are the most commonly used tests to help confirm a
diagnosis of Lyme disease and monitor its treatment. Antibody testing may
also be done on fluid from the spine or from a joint.
It may take up to 2 months after becoming infected before antibodies can
be detected in a blood test. Once formed, antibodies usually persist for
many years, even after successful treatment of the disease. Finding antibodies
to the Lyme disease bacteria does not indicate whether you were infected
recently or sometime in the past.
There are three types of antibody tests to detect Lyme disease.
Enzyme-linked immunosorbent assay (ELISA). This common and rapid
test to detect Lyme disease antibodies is considered the most sensitive
screening test for Lyme disease.
Indirect fluorescent antibody (IFA). This test also screens for
Lyme disease antibodies, but it may produce false results more often than ELISA.
Western blot test. This test also detects Lyme disease antibodies
and can confirm the results of an ELISA or IFA test. It is most often done to
detect a chronic Lyme disease infection. Antibody testing should be done in a
two-step process, using either the ELISA or IFA followed by the Western blot
test. ELISA is considered a more reliable and accurate test than IFA, but IFA
may be used if ELISA is not available. The Western blot test (which is a
more specific test) should be done in all people who have tested positive or
borderline positive (equivocal) in an ELISA or IFA test.
Other tests
Polymerase chain reaction (PCR) test. Polymerase chain reaction (PCR)
testing detects the genetic material (DNA)
of the Lyme disease bacteria. PCR testing may be useful for identifying a
current (active) infection if you have arthritis that does not improve with
antibiotic treatment. PCR testing is not done as frequently as antibody testing
because it requires technical skill and expensive equipment. Also, standards
have not yet been developed for PCR testing and there is a risk of
false-positive
test results.
Skin culture. A skin culture evaluates a tissue sample for the
bacteria that causes Lyme disease. It may take several weeks for test results to
come back. For this reason, antibody testing is done more frequently than a
tissue culture.
Why It Is Done
A test for Lyme disease is done to help confirm a diagnosis of Lyme disease.
Initial symptoms of Lyme disease include an expanding red skin rash at the site
of the tick bite. The
rash may look like a bull's-eye, with a pale center area surrounded by a
bright red rim. The rash usually fades in 3 to 4 weeks, but it may return.
Initial symptoms may also include fatigue, headache, stiff neck, fever, chills,
and muscle and joint pain. Symptoms of chronic Lyme disease infection include
joint pain, stiffness, and problems with the heart, brain, or nerves.
Testing is most accurate when you have
risk factors for Lyme disease or symptoms of the disease.
How To Prepare
There is no special preparation for this test.
Results
A Lyme disease blood test detects
antibodies to the
Lyme disease bacteria Borrelia burgdorferi. The results of a Lyme
disease test to detect antibodies (ELISA, IFA, Western blot) may be expressed 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.
NormalNormal values may vary from lab to lab.
Lyme disease test No antibodies to Lyme disease bacteria are detected.
The IFA test indicates no infection if the titer is less than 1:256.
The polymerase chain reaction (PCR) test does not detect any Lyme disease
bacteria
DNA.
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 indicates that you do
not have a Lyme disease infection.
The result is a
false negative. This is more likely with the antibody tests than with PCR.
Reasons for a false-negative result include:
You have not yet developed antibodies to the Lyme disease bacteria. The
infection may be present, but it is too early to detect 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 Lyme disease test Antibodies to Lyme disease bacteria are found.
For the IFA test, a titer equal to or greater than 1:256 is considered positive.
The polymerase chain reaction (PCR) test detects Lyme disease bacteria
DNA.
An abnormal, or positive, test for Lyme disease can mean one of the following:
If antibodies are detected, you may either have Lyme disease now or had the
illness in the past.
Once infected with Lyme disease, the antibodies to the bacteria usually remain
in the body for life.
If Lyme disease bacterial DNA is detected, you most likely have an active Lyme
disease infection. However, the PCR test will also detect the DNA of dead Lyme
disease bacteria.
The result is a
false positive. Sometimes an antibody test for Lyme disease detects
antibodies to other bacteria (such as
syphilis bacteria) or viruses (such as the
Epstein-Barr virus or the
human immunodeficiency virus, HIV).
The test
may also detect antibodies that
develop as part of an immune response against the body's own tissues (autoimmune
disease such as
rheumatoid arthritis or
lupus). It can be difficult to tell whether the antibodies detected have
developed in response to the bacteria that cause Lyme disease. The PCR
test may be done to confirm an infection if you have a positive antibody test
result.
What Affects the Test
Factors that can interfere with your test and the accuracy of the results
include:
A high amount of
rheumatoid factor in the blood.
High
lipid levels.
What To Think About
Because false-positive and false-negative Lyme disease test results are not
uncommon, this test can add confusion to the diagnosis of the illness.
Also, only about 60% of people who have Lyme disease develop antibodies within 3
weeks of becoming infected. The decision about when to use blood tests
to detect Lyme disease should depend on whether your health professional
strongly suspects Lyme disease and whether the test result will alter the course
of treatment. Testing should be done only if you have
risk factors for Lyme disease or
symptoms of Lyme disease and test results are likely to affect treatment
decisions. If you have symptoms of Lyme disease but test results are negative,
treatment should not be delayed.
A urinary antigen test to check for Lyme disease is not a useful test, and
it is not considered scientifically valid in the diagnosis of Lyme disease.
Detecting antibodies to the bacteria that cause Lyme disease does not always
mean that the infection is active. It merely means that you were infected at one
time. This makes it difficult to distinguish between an active and a past
(inactive) infection. The polymerase chain reaction (PCR) test may
determine whether an active Lyme disease infection is present.
Credits
Author Jan Nissl, RN, BS
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Tracy Landauer
Primary Medical Reviewer
Adam Husney, MD
- Family Medicine
Specialist Medical Reviewer
W. David Colby, MSc, MD, FRCPC
- Infectious Disease
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MDL Does Tissue Testing for Lyme & Bartonella
Medical Diagnostic Laboratories
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Mt. Laurel, NJ 08054
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Office: 856.608.1696
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