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.
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 is a rapid test to identify Lyme disease antibodies.
- 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 should be done for all people who've had a positive (or borderline positive) 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. The PCR test is a blood or urine test, but can also be done on fluid from the spine or from a joint.
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.
An antibody test checks to see if you've had an infection from a bacteria that causes Lyme disease.
- A normal (negative) test means that no Lyme disease antibodies are found.
- An abnormal (positive) test means that Lyme disease antibodies are found.
The polymerase chain reaction (PCR) test may be done to confirm a Lyme infection if you have a positive antibody test result.
- A negative PCR test means the test didn't detect Lyme disease bacteria DNA.
- A positive PCR test means the test detected 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.
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.