American Board of Internal Medicine (ABIM) Certification Practice Exam

How is late disseminated Lyme disease with oligoarticular arthritis diagnosed?

1. Serologic testing, PCR of synovium or synovial fluid

2. Joint aspiration and culture

3. Physical examination alone

4. CT scan of the joints

The correct answer is: Serologic testing, PCR of synovium or synovial fluid

The diagnosis of late disseminated Lyme disease, particularly when presenting with oligoarticular arthritis, mainly relies on serologic testing and, when necessary, PCR of synovial tissue or synovial fluid. Serologic testing is pivotal because it helps detect antibodies against the causative agent, Borrelia burgdorferi, indicating past or ongoing infection. Examination of synovial fluid through PCR provides a more direct method to identify the presence of the bacteria, especially in cases where serologic results may be ambiguous or when early antibiotic treatment has impaired antibody response. In contrast, joint aspiration and culture may potentially identify infectious agents in acute cases; however, Borrelia is challenging to culture and does not commonly yield positive results in cases of Lyme arthritis. Relying solely on physical examination is insufficient for a definitive diagnosis, as the signs and symptoms of Lyme disease can overlap with other musculoskeletal disorders. Moreover, imaging techniques like CT scans are not typically used for this diagnosis, as they do not provide direct evidence of infection and are not diagnostic for Lyme disease itself. Thus, the use of serologic testing and targeted PCR analysis emerges as the most effective diagnostic approach for late disseminated Lyme disease with oligoarticular arthritis.