American Board of Internal Medicine (ABIM) Certification Practice Exam

Which of the following is characteristic of eosinophilia in ABPA?

1. Below 400 uL

2. Above 600 uL

3. Below 200 uL

4. Above 500 uL

The correct answer is: Above 500 uL

Eosinophilia in allergic bronchopulmonary aspergillosis (ABPA) is typically characterized by elevated eosinophil counts, often exceeding 500 uL. This increase in eosinophils is an important marker for the condition, as it reflects the immune response to the presence of Aspergillus fumigatus, the fungus at the center of ABPA. In patients with ABPA, eosinophil counts can often be found in the range of 500 to 1500 cells per microliter, depending on the severity of the allergic reaction. This elevated eosinophilic response contributes to the respiratory symptoms and impaired lung function that characterize ABPA. Counts below 400 uL or 200 uL would not typically signify eosinophilia, as those levels are generally considered within the normal range. Being above 600 uL also indicates a significant eosinophilic response, but the threshold of 500 uL is a clear demarcation for defining eosinophilia in this clinical context, making the option of above 500 uL the most characteristic of eosinophilia associated with ABPA.