Lyme Disease and Related Tick-Borne Infections - Diagnosis

Diagnosis

Lyme disease is usually diagnosed based on symptoms and evidence of possible exposure to ticks. A diagnosis of Lyme disease is straightforward if the patient meets the following criteria:

• Lives in an area of tick-infestation
• Has the tell-tale bulls-eye rash (erythema migrans)
• Has other symptoms (headache, joint aches, malaise, flu-like symptoms)

If the patient meets these criteria, treatment is often started without confirming the diagnosis with laboratory tests.

Blood Tests for Antibodies

Blood tests for detecting antibodies to B. burgdorferi may give false results during the early stages of the disease. They are more accurate if used at least a month after the initial infection. The U.S. Centers for Disease Control (CDC) recommends a two-step process for Lyme disease blood tests:

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• ELISA or IFA Test. The first tests used are either enzyme-linked immunosorbent assay (ELISA) or an indirect fluorescent antibody (IFA) test. ELISA is the immune test used most often for Lyme disease. (The IFA test is less accurate but may be used when ELISA isn't available.) ELISA measures antibodies that are directed against the B. burgdorferi spirochete. A newer variant is a rapid test (PreVue) that can provide results within an hour. Positive results from any of these tests still require confirmation with a Western blot test. Negative results do not require further testing.
• Western Blot. If the ELISA or IFA test is positive or uncertain, it is followed by the Western blot test. This test is more accurate and is very helpful in confirming the diagnosis. The Western blot creates a visual graph showing bands of different colors or shading that laboratories use to interpret the immune response.

The CDC recommends only these tests. Other tests -- such as urine antigen, immunofluroescent staining, and lymphocyte transformation -- do not have enough scientific evidence to support their use.

If the patient does not have any symptoms of Lyme disease, these tests are not recommended. These tests should not be used to make a diagnosis of Lyme disease in patients who do not have obvious symptoms or findings of the disease. This is because both false positive and false negative results are common with these tests.