American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the preferred method to determine the microbiologic cause of vertebral osteomyelitis?

1. Blood cultures

2. CT-guided needle aspiration biopsy

3. Magnetic resonance imaging (MRI)

4. X-rays

The correct answer is: CT-guided needle aspiration biopsy

The preferred method to determine the microbiologic cause of vertebral osteomyelitis is through CT-guided needle aspiration biopsy. This technique allows for direct sampling of the affected tissue, which is crucial for obtaining specific cultures that can identify the causative organism. Blood cultures, while useful, often do not provide a definitive diagnosis since not all cases of vertebral osteomyelitis will result in a positive blood culture, and it may miss localized infections. Imaging modalities like MRI play an essential role in diagnosing vertebral osteomyelitis by providing detailed images of the spine, including soft tissue and bone changes, but they do not provide microbiological information. X-rays are typically less sensitive for early detection of osteomyelitis and, like MRI, do not directly reveal the causative organism. Overall, the biopsy enables both microbiological analysis and histological examination, making it the most effective method for diagnosing the specific infectious agent involved in vertebral osteomyelitis.