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Serologic Diagnosis of Lyme Disease



Diagnosis of Lyme Disease

Slide 8

May 2008

To answer this question I’d like for us to review the algorithm recommended by the CDC for serologic testing.

Currently the CDC recommends a two-step approach for the serologic diagnosis of Lyme disease. In the first tier of testing the specimen is tested by a highly sensitive screening assay such as enzyme immunoassay. If the result of the screening EIA is negative, the report should go out as negative and no further testing is generally required with the present specimen. However, in the case of short disease duration it may be beneficial to submit a follow-up specimen in 7 to 14 days if clinically indicated.

If, on the other hand, the result of the screening assay is positive or equivocal, the specimen should then be tested by Western blot for IgM and IgG class antibodies. Currently the criteria for determining whether a Lyme Western blot is positive or negative depends on the total number of diagnostic bands determined to be present on the test strip.

For instance, an IgM Western blot is positive if at least 2 of the 3 diagnostic bands are present and for IgG the laboratory must observe at least 5 of the 10 diagnostic bands for a positive result. Specimens meeting these criteria are reported as positive and these results would support a clinical suspicion of Lyme disease.

If these criteria are not met, the result is reported as negative and no further testing is required except again in the setting of short disease duration. If this is the case a follow-up specimen could be tested in 1 – 2 weeks if clinically indicated.

I just want to empathize one additional point regarding Lyme Western blot before we move on. The criteria for Lyme Western blot were established to guide the interpretation of serum samples and should not be applied when interpreting CSF results. To assist in the interpretation of CSF Western blot results, we recommend that a serum sample collected at or near the time of the spinal tap be submitted along with the CSF specimen so that both may be tested in parallel.

Diagnosis of Lyme Disease

 


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