Lyme Disease Diagnosis
Diagnosis is clinical and is based primarily on recognition of the typical symptoms of Lyme disease in a person who lives in a high-risk area. Doctors like to have hard evidence to back up their opinions, but testing is not an exact science: the tests for Lyme disease may sometimes be negative in cases where disease is actually present, and false positive tests, though less common, are also possible. Therefore, experienced doctors recommend that Lyme disease be diagnosed clinically, meaning they base the diagnosis on an evaluation of your risk and your symptoms.
To view the Center For Disease Control's, "Lyme is a clinical diagnosis", click here.
People with chronic Lyme disease may be misdiagnosed with more familiar conditions with symptoms that mimic Lyme disease.
Since scientists have not figured out the cause of these diseases and treatment does not call for antibiotics, the underlying Lyme infection is allowed to progress unchecked.
Some doctors consider a bull’s-eye rash diagnostic and don’t require further tests. Others, however, require laboratory confirmation before treatment.
Culture is the “gold standard” test for identifying bacteria. A sample of the organism is taken from the patient is allowed to grow in a medium and then identified. Culture is accepted as proof of infection. While culture is used to diagnose many infections, it is not practical for Lyme because the bacteria grow too slowly. There are no commercially available culture tests for Lyme.
The most common tests measure the patient’s antibody response to infection. When your body is invaded by the Lyme spirochetes, your immune system makes antibodies to fight the infection. Tests that measure antibody levels are indirect tests because they measure the body’s response to infection rather than the presence of the bacteria themselves.
During the first 4-6 weeks after exposure, most people have not developed the antibody response that the test measures. Treatment should not be delayed pending a positive test result if the suspicion of Lyme disease is high (exposure, tick bite, possible rash).
Two primary antibody tests are used to diagnose Lyme disease, the ELISA and the western blot. Doctors commonly order an ELISA first to screen for the disease and then confirm the disease with a western blot. However, current ELISA tests are not sensitive enough for screening and may miss over half the true cases. Because of this, the best antibody test to use for diagnosis is the western blot. To learn more about the tests, click here.
The read-out from the western blot looks like a bar code. The pattern produced by running the test with your blood is compared to a template pattern that represents known cases of Lyme disease. If your blot has bands in the right places, and the right number of bands, it is positive. Some of the bands are more significant than others and your doctor may decide you have Lyme disease even if your western blot does not have enough bands or the right bands to be reported to the Centers for Disease Control and Prevention (CDC) for surveillance purposes.
Different laboratories use different methods and criteria, so you can have a positive test result from one lab and a negative test result from another. Lyme disease is known to inhibit the immune system and twenty to thirty percent of patients have falsely negative antibody tests. To view interpretation of the western blot test, click here.
To view Seronegativity Fast Facts, click here.
Two other tests that may be used to diagnose Lyme disease are PCR and antigen detection tests. Polymerase chain reaction (PCR) multiplies a key portion of DNA from the Lyme bacteria so that it can be detected. While PCR is highly accurate when the Lyme DNA is detected, it produces many false negatives. This is because Lyme bacteria are sparse and may not be in the sample tested. Antigen detection tests look for a unique Lyme protein in fluid (e.g. blood, urine, joint fluid). Sometimes people whose indirect tests are negative are positive on this test.
CALDA recommends that you use a CLIA- and Medicare-approved lab that specializes in testing for tickborne diseases and reports all bands on the western blot. The healthcare professional ordering the test must ask the lab to report all bands except in the case of IGeneX, which automatically reports all bands. Blots may still vary in sensitivity.
IGeneX www.igenex.com 800-832-3200
Stony Brook www.path.sunysb.edu/labs/ticklab/ticklab.htm
MDL www.mdlab.com 877-269-0090