American Board of Internal Medicine (ABIM) Certification Practice Exam

What method is used for diagnosing viral meningitis?

1. Blood tests only

2. CSF culture

3. Polymerase chain reaction (PCR)

4. Radiology imaging

The correct answer is: Polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) method is the preferred diagnostic tool for viral meningitis due to its sensitivity and specificity. PCR allows for the rapid detection of viral nucleic acids directly from cerebrospinal fluid (CSF) samples. This is particularly important because viral meningitis can be caused by various viruses, and traditional cultures may take longer or might not yield results for all viral pathogens. When a patient presents with signs and symptoms suggestive of meningitis, obtaining a CSF sample through lumbar puncture is crucial. The CSF is then analyzed using PCR to identify viral pathogens such as enteroviruses, herpes simplex virus, and others. This method not only identifies the causative virus but also helps differentiate viral meningitis from bacterial meningitis, which requires different treatment approaches. While blood tests can provide ancillary information about the patient's overall health and immune response, they are not specific enough to diagnose viral meningitis. CSF cultures, although historically used, have limitations in sensitivity for viral detection compared to PCR. Radiology imaging may assist in ruling out other causes of neurological symptoms, but it does not directly diagnose viral meningitis. Thus, PCR stands out as the most effective method for the definitive diagnosis of viral meningitis.