Lyme Disease and Related Tick-Borne Infections - Diagnosis

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The CDC recommends only these tests. In 2005, the CDC warned against tests -- such as urine antigen, immunofluroescent staining, and lymphocyte transformation -- that do not have enough scientific evidence to support their use.

Accuracy of the Tests. These tests are very expensive, and none are completely accurate in either identifying Lyme or ruling it out. They should never be used to make a primary diagnosis of Lyme disease in patients who do not have obvious symptoms of the disease.

Either false positive and false negative results are common with these tests.

False positive results occur when the test suggests the presence of the disease, but the person does not actually have an active infection. This may occur in different ways:

• The antibodies to the infectious organism triggering the antibodies are not the Lyme spirochetes. Other organisms that can trigger such antibodies include syphilis and relapsing fever. Dental infections may trigger a false positive response.
• The patient may have been infected with Lyme disease previously and harbor antibodies to the disease.

False negative results are those that miss the actual presence of the disease. These results are also common. (If the results are negative but Lyme disease is highly suspected, the doctor will probably prescribe antibiotics anyway.) False negative results occur for a number of reasons:

• The test is taken too early in the course of Lyme disease. In such cases, the antibodies that fight the spirochete might not have reached a level that is high enough to be detected. (Only about 20 - 30% of patients can be identified using immune system tests in the first 2 - 4 weeks. By the fourth week, up to 80% of patients will have detectable antibodies.)
• The patient has taken certain medications, such as steroids or certain anti-cancer drugs, which reduce the immune system's ability to produce antibodies, including those in response to Lyme disease.
• There are too many infection-fighting antibodies attached to the bacteria. In this case, there are not enough loose antibodies in the blood sample to trigger a response.
• The laboratory itself has set its sensitivity point too high. Some laboratories establish a standard of very high antibody levels before the test results will trigger a finding of Lyme disease. (They do this to avoid too many false-positive responses.) In so doing, however, their tests may miss the disease in patients with lower antibody levels. A related diagnostic problem concerns the possibility of missing persistent Lyme disease after antibiotic treatments, when antibody levels would be low.