Lyme Disease Test
Lyme disease can be hard to diagnose because its symptoms are similar to those of many other illnesses. If you and your doctor think you have Lyme disease, your doctor will do a careful medical history and physical exam. Antibody tests can sometimes be used to help identify Lyme disease. Other tests may be done in certain situations.
Antibody tests are the most commonly used tests to help identify Lyme disease. 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 stay in your system for many years, even after successful treatment of the disease. Finding antibodies to the Lyme disease bacteria does not tell whether you were infected recently or sometime in the past.
There are two types of antibody tests to detect Lyme disease.
- Enzyme-linked immunosorbent assay (ELISA). This common and rapid test to identify Lyme disease antibodies is the most sensitive screening test for Lyme disease.
- Western blot test. This test also identifies Lyme disease antibodies and can confirm the results of an ELISA test. It is most often done to detect a chronic Lyme disease infection.
Antibody testing should be done in a two-step process, using the ELISA followed by the Western blot test. The Western blot test (which is a more specific test than the ELISA) should be done in all people who have tested positive or borderline positive (equivocal) in an ELISA test.
Polymerase chain reaction (PCR) test. Polymerase chain reaction (PCR) testing detects the genetic material (DNA) of the Lyme disease bacteria. PCR testing may be used to identify a current (active) infection if you have symptoms of Lyme disease that have not gotten better with antibiotic treatment. PCR testing is not done as often 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.
Why It Is Done
A Lyme disease test is done to diagnose Lyme disease in people who have symptoms of Lyme disease. Symptoms may include:
- An expanding red rash with a pale center. This is sometimes called a "bull's-eye" rash.
- Extreme tiredness.
- Headache and stiff neck.
- 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
In general, there's nothing you have to do before this test, unless your doctor tells you to.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Test results are usually available in 1 to 2 weeks.
No antibodies to Lyme disease bacteria are found.
The polymerase chain reaction (PCR) test does not find any Lyme disease bacteria DNA.
Antibodies to Lyme disease bacteria are found.
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. Once you have a Lyme disease infection, antibodies to the bacteria will usually stay in your body for the rest of your life.
- If Lyme disease bacteria DNA is found, you probably have an active Lyme disease infection.
- 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.
Current as of: September 23, 2020
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Christine Hahn MD - Epidemiology
W. David Colby IV MSc, MD, FRCPC - Infectious Disease
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