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
You do not need to do anything before you have this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
How It Is Done
The health professional taking a sample of your blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.
How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
- You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
- In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
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.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- You have a viral infection, such as Epstein-Barr virus or HIV.
- You have another bacterial infection, such as syphilis.
- You have high lipid levels.
What To Think About
- It may be hard to tell if you have Lyme disease. False-positive and false-negative Lyme disease test results are common. Many people do not make antibodies to Lyme disease bacteria for up to 8 weeks after being infected.
- Doctors often do not rely on test results alone when recommending treatment for a person who may have Lyme disease. Treatment is often based on a person's symptoms, the time of year, having a tick bite, and other risk factors for Lyme disease.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- National Institutes of Health, U.S. Department of Health and Human Services (2008). Lyme Disease: The Facts, the Challenge (NIH Publication No. 08-7041). Available online: http://www.niaid.nih.gov/topics/lymeDisease/Documents/lymedisease.pdf.
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.