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Sunday, May 01, 2005

Testing for Lyme

Q: HOW IS LYME DISEASE DIAGNOSED?
A: Lyme is diagnosed clinically, as no currently available test, no matter the source or type, is definitive in ruling in or ruling out infection with these pathogens, or whether these infections are responsible for the patient's symptoms. The entire clinical picture must be taken into account, including a search for concurrent conditions and alternate diagnoses, and other reasons for some of the presenting complaints. Often, much of the diagnostic process in late, disseminated Lyme involves ruling out other illnesses and defining the extent of damage that might require separate evaluation and treatment.


Q: WHAT TESTS ARE AVAILABLE?

A: A variety of tests are available. Many doctors who are unfamiliar with Lyme disease may only use the test available in their local laboratory. In many cases this is the Lyme ELISA (EIA) or IFA, often-called “Titer Test”. These tests measure a patient's antibody, IgM and/or IgG, in response to exposure to the Lyme bacteria. By today's standards, these tests are not very sensitive.

The Western Blot tests (IgG and/or IgM) are much more sensitive and specific than the above titer tests. With the Western Blot, the laboratory can actually visualize the exact antibodies you are making to the Lyme bacteria. In some cases the laboratory may be able to say that your “picture of Lyme antibodies” is consistent with early disease, with persistent/recurrent disease or maybe even with long-term disease. Not all patients have antibodies at all times when they are tested. Antibodies are more commonly detected within the first year after infection, although reinfection may cause a significant increase in antibodies. At most, only 70% of patients have antibodies that are detectable by Western Blot testing.

PCR (Polymerase Chain Reaction) test detects the presence of the DNA of the Lyme bacteria. PCR tests have more sensitivity early in the disease before patients have received antibiotics. This is a relatively expensive test. The best specimen to test has not been defined. The test can be preformed on whole blood, serum, urine, synovial fluid and spinal fluid.


Q: WHICH TEST IS BEST?
A: Physicians are often asked what is the best test for Lyme disease? That is a difficult question because there is no one best test. Lyme disease is complicated. It may mimic or masquerade as arthritis, muscle aches, flu, cardiac disease, chronic fatigue, fibromyalgia, multiple sclerosis, autoimmune diseases such as lupus and rheumatoid arthritis, or other illnesses. Some of these diseases require multiple tests and so does Lyme. At a minimum, the IgM and IgG Western Blots for B. burgdorferi need to be ordered. If your physician suspects an autoimmune disease (i.e., systemic lupus or rheumatoid arthritis), an ANA or rheumatoid factor test may be needed.

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