American Board of Internal Medicine (ABIM) Certification Practice Exam

How many eosinophils per high-power field (hpf) are needed for the diagnosis of eosinophilic esophagitis?

1. 10 eosinophils/hpf

2. 15 eosinophils/hpf

3. 20 eosinophils/hpf

4. 25 eosinophils/hpf

The correct answer is: 15 eosinophils/hpf

The diagnosis of eosinophilic esophagitis (EoE) is based on the observation of eosinophils in the esophageal tissue. A significant finding is established at the threshold of 15 eosinophils per high-power field (hpf) when examined histologically. This level indicates an abnormal influx of eosinophils, which is characteristic of EoE, distinguishing it from other conditions that may involve eosinophils in the esophagus but do not meet the diagnostic criteria for this specific disorder. The importance of this measurement lies in the implication that eosinophils, a type of white blood cell usually associated with allergic reactions and asthma, play a major role in the inflammatory process seen in EoE. The presence of 15 eosinophils/hpf serves as a critical marker in both diagnosing and guiding the therapeutic approach to managing the condition, as eosinophilic infiltration is symptomatic of an underlying allergic process. In contrast, thresholds of eosinophils that are either lower than 15 or markedly higher may denote different interpretations and clinical considerations. Thus, specifying 15 eosinophils per hpf is essential for establishing a diagnosis of eosinophilic esophagitis.