Lyme Disease and Related Tick-Borne Infections - Diagnosis

Diagnosis

Proper diagnosis of Lyme disease is important. 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
• Has other symptoms (headache, joint aches, malaise, flu-like symptoms)

If the patient meets all the criteria, except the rash, then the doctor may undertake the enzyme-linked immunosorbent assay (ELISA) or the Western Blot test.

Culture

In some cases, if the patient seeks a diagnosis within the first 2 - 3 weeks, the doctor may take a sample of the skin or of the blood. If Lyme spirochete is present, it may be identified in the laboratory in a culture medium (a substance in which the organism can thrive and reproduce). This is necessary only if a doctor suspects Lyme but the diagnosis is not clear.

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Immune Testing

If the infection is not obvious from the patient's history and physical symptoms but Lyme disease is suspected, the doctor may run tests for evidence of specific factors that suggest infection with B. burgdorferi. Such factors include:

• Proteins referred to as Osps. These proteins (referred to as Osp A through F) coat the outer surface of the B. burgdorferi spirochete and then attach to human cells after infection.
• Antibodies that attack these Osps. Antibodies are the weapons of the immune system that are launched when foreign invaders (called antigens) are detected. In the case of Lyme disease, these antigens are the Osps.

Specific Tests.

The U.S. Centers for Disease Control (CDC) recommends a two-step process for Lyme disease blood tests:

• ELISA and Other Initial Tests. 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 any of these tests is positive or uncertain, then they are followed by the Western immunoblot (WB), which 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 experts use to interpret the immune response.