American Board of Internal Medicine (ABIM) Certification Practice Exam

What diagnostic method is used for late disseminated Lyme disease with encephalopathy or encephalomyelitis?

1. Serologic testing, intrathecal antibody, CSF PCR

2. MRI of the brain

3. Chest X-ray

4. Electroencephalogram (EEG)

The correct answer is: Serologic testing, intrathecal antibody, CSF PCR

The use of serologic testing, intrathecal antibody assessment, and CSF PCR (polymerase chain reaction) is the appropriate diagnostic method for late disseminated Lyme disease, particularly when neurological symptoms like encephalopathy or encephalomyelitis are present. In the context of Lyme disease, serologic testing helps identify antibodies against Borrelia burgdorferi, the bacterium that causes Lyme disease. However, in cases where neurological involvement is suspected, such as encephalopathy, additional testing is necessary. Intrathecal antibody testing can demonstrate the production of antibodies within the central nervous system, often indicating active disease. CSF PCR can directly detect the genetic material of the bacteria in cerebrospinal fluid, providing definitive evidence of Lyme disease affecting the central nervous system. Other diagnostic methods mentioned are not as appropriate for this condition. While an MRI of the brain can reveal changes associated with Lyme disease, it does not confirm the diagnosis and instead plays a role in ruling out other causes of encephalopathy. A chest X-ray is not relevant for diagnosing Lyme disease, and an electroencephalogram (EEG) is mainly used to assess electrical activity in the brain but does not provide diagnostic clarity for infectious etiologies like Lyme disease.