Testing for Lyme disease usually involves a two-step blood test process recommended by the CDC. The first test is an ELISA (enzyme-linked immunosorbent assay) that detects antibodies against the Lyme disease bacteria. If this test is positive or unclear, a second test called a Western blot or a second ELISA is done to confirm the diagnosis. These tests detect antibodies, which take several weeks after infection to develop, so early infection may yield false negatives. In some cases, cerebrospinal fluid testing may be done if nervous system involvement is suspected. Here is a detailed overview:
Two-Step Blood Testing Process
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First Test: ELISA
Detects antibodies to Borrelia burgdorferi, the bacteria causing Lyme disease. This test may be negative if performed too soon after infection because antibodies take time to develop. -
Second Test: Western Blot or second ELISA
Used to confirm positive or equivocal ELISA results by checking for antibodies reacting to specific parts of the bacteria.
Timing and Accuracy
- Antibodies typically appear 2-4 weeks after infection (IgM) and 4-6 weeks (IgG), peaking at 6-8 weeks.
- Early Lyme disease diagnosis may rely on clinical signs such as the characteristic erythema migrans rash rather than blood tests, due to possible false negatives early on.
- Testing negative initially may warrant retesting in 2-4 weeks if suspicion remains high.
Additional Testing
- CSF Testing (Cerebrospinal Fluid)
Performed via lumbar puncture if neurological symptoms suggest Lyme involvement in the nervous system.
Limitations
- Antibody tests can remain positive for months or years even after successful treatment.
- False positives can occur due to other conditions like syphilis, rheumatoid arthritis, and Epstein-Barr virus.
- Early antibiotic treatment may prevent antibody development and affect test results.
In summary, Lyme disease is primarily diagnosed through a two-step antibody blood test (ELISA followed by Western blot if needed), combined with clinical evaluation and exposure history. Early diagnosis may require clinical judgment as tests can be negative initially after infection.
