From the Guidelines
For suspected Lyme arthritis, I recommend a two-tier testing approach starting with an enzyme-linked immunosorbent assay (ELISA) to detect antibodies against Borrelia burgdorferi, followed by a Western blot test if the ELISA is positive or equivocal, as outlined in the 2016 guidelines for laboratory diagnosis of Lyme disease 1. This approach is supported by the most recent and highest quality study, which emphasizes the importance of proper interpretation of laboratory tests in the context of symptoms and timing of illness. Some key points to consider when interpreting test results include:
- The sensitivity of two-tiered testing is low (30%–40%) during early infection, but increases to 70%–100% for disseminated Lyme disease 1
- Specificity is high (>95%) during all stages of disease 1
- Patients typically develop antibodies within 4-6 weeks after infection, so testing too early may yield false negatives
- If clinical suspicion remains high despite negative serology, consider repeating tests in 2-4 weeks Additionally, synovial fluid analysis may be helpful to rule out other causes of arthritis, including crystal analysis and culture, as recommended by the 2020 guidelines for the prevention, diagnosis, and treatment of Lyme disease 1. It is essential to perform testing before initiating antibiotics to avoid false negative results. The diagnosis of Lyme arthritis relies on both clinical presentation (typically monoarticular or oligoarticular arthritis affecting large joints, especially the knee) and laboratory confirmation of B. burgdorferi infection, as symptoms alone are not specific enough for definitive diagnosis.
From the Research
Initial Testing for Lyme Arthritis
To diagnose Lyme arthritis, the following initial testing is recommended:
- Enzyme-linked immunosorbent assay (ELISA) for IgG and IgM antibodies against Borrelia burgdorferi 2, 3, 4
- Western blot analysis to confirm the results of the ELISA, particularly when there are low antibody titers 2, 3, 4
- Synovial fluid analysis, including PCR for B. burgdorferi, to detect the presence of the bacteria in the joint fluid 5
Interpretation of Test Results
The interpretation of test results is crucial in diagnosing Lyme arthritis:
- A positive ELISA result should be confirmed by Western blot analysis 2, 4
- IgG antibody levels of 200 IU/ml or higher may be sufficient to detect antibodies to B. burgdorferi, and a confirmatory immunoblot may be omitted 4
- The presence of IgM antibodies may indicate early infection, while IgG antibodies may indicate later stages of infection 2, 3
Clinical Considerations
Clinical considerations are essential in diagnosing Lyme arthritis:
- A thorough medical history and physical examination should be performed to rule out other causes of arthritis 5
- The clinical presentation of Lyme arthritis may vary, but it often presents as chronic knee monoarthritis 5
- The sensitivity of synovial fluid PCR for B. burgdorferi may be low, and a negative result does not rule out the diagnosis 5