Lyme Disease Diagnosis
Lyme disease diagnosis should be based on a history of tick bite or exposure in Lyme disease endemic areas, clinical findings such as the presence of a large circular rash, examination by a physician for other symptoms, and laboratory tests. The most reliable indication of acute or early stage Lyme disease is the presence of a large circular rash, called erythema migrans, which takes 2-3 weeks to develop after a tick bite. Erythema migrans (EM) occurs in 60-80% of Lyme disease patients. It is defined by the CDC as a skin lesion that typically begins as a red macule or papule and expands over a period of days to weeks to form a large round lesion. A single primary lesion must reach at least 5 cm in size. Annular reddened lesions occurring within several hours of a tick bite represent hypersensitivity reactions and do not qualify as EM. Other nonspecific symptoms such as fever, malaise, headache, muscle aches, and joint aches may also be present in addition to the EM. If you develop any of the symptoms and recall being bitten by a tick or have traveled to or live in an area that is endemic for Lyme disease, discuss your suspicions of Lyme disease with your physician.
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For patients showing an EM lesion, a skin punch biopsy, taken at the edge of the EM lesion, may be performed for culture of Borrelia burgdorferi, the causative agent of Lyme disease. Such specimens must be taken PRIOR to antibiotic therapy. MDCH provides this test free of charge to Michigan residents. Any Michigan physician can submit specimens to the MDCH laboratory. Click here to view MDCH Laboratory Submission Form.
Serologic testing is also available but should used to support other diagnostic information, such as history and clinical findings. Serologic testing can provide valuable supportive diagnostic information in patients with clinical findings that suggest later stage disseminated Lyme disease. Late stage diagnosis is still less reliable, however, and testing should be used selectively for patients from populations with a relatively high prevalence of Lyme disease or those who have specific clinical findings suggestive of Lyme disease.
For any serologic testing that is performed, a two-step standardized blood test should be utilized. It is recommended that the first step test be a sensitive test, usually an ELISA. If the first step test is positive or equivocal, then it should be confirmed with the more specific Western Blot. (Enzyme immunoassays sometimes produce false-positive results because of cross-reactive antibodies, hence the recommendation for two-step testing.) A Western Blot is more specific because it utilizes protein bands specific to Borrelia burgdorferi. If specific antibodies to the individual protein bands are present, they will bind to the corresponding bands. For patients presenting with acute signs of Lyme disease where serologic testing is to be performed within 30 days of onset of clinical illness, it is recommended that IgM specific WB testing be performed. For patients needing testing greater than 30 days from the disease onset or with symptoms consistent with late stage Lyme disease, it is recommended that IgG specific WB testing be performed. All testing methods may not be standardized among all laboratories; therefore, a final diagnosis should not be made solely on serological results. Other factors that must be considered include the type of illness and the opportunity for exposure to Lyme-disease-carrying ticks.