Diagnosing Lyme Disease

What is Lyme Disease?

Lyme disease, or Lyme borreliosis, is an infectious disease caused by the bacteria Borrelia. In North America, Borrelia burgdorferi and Borrelia mayonii are the typical cause of Lyme disease. In Europe and Asia, Borrelia afzelii and Borrelia garini are the typical cause of Lyme disease. The bacteria is spread to humans via the bite of an infected tick, a deer tick or black legged tick.

Diagnostic Difficulties

Lyme Disease can be difficult to diagnosis. Many of the common symptoms, such as headache, fatigue, or joint pain, are similar to symptoms experienced in a variety of other conditions. The most distinctive symptom, the bullseye rash or erythema migran, does not appear on everyone who has Lyme disease. At least 25% of individuals with Lyme disease do not experience the rash(source1). Diagnostic tests that are currently available have limitations; they cannot diagnosis early Lyme Disease, as it takes time for antibodies that the test measures to appear.

Test for Lyme Disease

There are two common tests which are generally used for Lyme disease, the ELISA test and the Western Blot Test.


This is a blood test that detects antibodies an individual's body makes in response to B. burgdorferi. It does not actually test for B. burgdorferi bacteria. If testing is done too early or too late, it can give a false negative test result.

Western Blot Test

This blood test was designed to be positive only if a person has been infected by B. burgdorferi. It detects two different classes of antibodies: IgM and IgG. IgM antibodies show up faster, within the first 4 weeks, but are more likely to give a false positive. Testing for IgG antibodies is more reliable, but IgG antibodies take up to 4-6 weeks to develop to the point in the body where there is enough to test. Up to 20% of Lyme disease cases can be missed by this test (source3).

In terms of testing, the CDC recommends that doctors who believe an individual may have Lyme disease run the ELISA test first. If the ELISA test comes back positive or is uncertain, then the Western Blot Test should be done. It should be noted that not all organizations agree with how the tests are used for ruling out Lyme disease, including the International Lyme and Associated Diseases Society (ILADS).

Important Factors for Making a Lyme Diagnosis

The following factors should be considered when diagnosing Lyme disease:

1. Tick bite & exposure risk. Even if an individual does not remember being bitten by a tick, this does not preclude the possibility of being diagnosed with Lyme disease. An individual’s activities (i.e. hiking, camping), where they live, and where they have travelled should be taken into consideration.

2. Rash / Erythema Migrans. This is a classic symptom of Lyme disease but it should be noted that the rash does not always appear as a “bullseye” and not every individual may experience the rash, even if they do have lyme disease. Other tick-borne infections can also cause rashes.

3. Other symptoms. Lyme disease symptoms can mimic those of many different disorders, including rheumatologic and neurologic conditions. Individuals who have long lasting cases of Lyme disease can be misdiagnosed with somatoform disorders.

4. Testing. If an individual has the erythema migrans rash and a history that matches Lyme disease, testing is generally not necessary. Testing can be used in other cases, remembering that testing too soon or too late can result in a false negative. A negative test result alone should not be the sole reason for ruling out a Lyme diagnosis.

Diagnosing Lyme disease is not simple. It requires assessing the individual’s history for possible tick exposure, assessing possible physical findings for symptoms of Lyme disease, and laboratory testing. The diagnosis is best made when considering all of these elements.

What Type of Doctor to see for a Diagnosis?

Individuals who suspect that they may have Lyme disease should seek a doctor who is familiar with Lyme disease. The International Lyme and Associated Diseases Society (ILADS) can provide a list of Lyme-aware doctors.

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