What is the clinical significance of an elevated absolute eosinophil (AEC) count?

From the Guidelines

An elevated absolute eosinophil count (AEC) above 1500 cells/μL is a key indicator of hypereosinophilic syndromes (HES) and warrants thorough clinical investigation to identify underlying causes and prevent potential organ damage. The clinical significance of an elevated AEC count is closely tied to the presence of eosinophilic infiltration and inflammation in various organs, including the esophagus, skin, lungs, heart, and nervous system 1.

Clinical Significance of Elevated AEC

Elevated AEC counts can be associated with a range of conditions, including:

• Hypereosinophilic syndromes (HES), characterized by marked eosinophilia (AEC >1500 cells/μL) and organ damage due to eosinophilic infiltration 1
• Eosinophilic esophagitis (EoE), a chronic immune/antigen-driven disease characterized by esophageal symptoms and eosinophilic inflammation in the esophagus 1
• Other gastrointestinal diseases, such as eosinophilic gastritis and eosinophilic enteritis, which may be associated with peripheral eosinophilia and esophageal involvement 1

Evaluation and Management

Evaluation of an elevated AEC count should include a thorough history focusing on travel, medications, and allergies, followed by targeted testing based on suspected etiology 1. Treatment targets the underlying cause rather than the eosinophilia itself, and may involve the use of topical steroids, diet exclusions, or other therapies depending on the specific condition diagnosed 1. Persistent unexplained eosinophilia requires monitoring as it may indicate developing conditions or potential for end-organ damage through eosinophilic infiltration and inflammation.

Key Considerations

• The presence of peripheral eosinophilia (AEC >1500 cells/μL) can help distinguish HES from isolated EoE, but other gastrointestinal diseases may also be associated with peripheral eosinophilia 1
• A thorough diagnostic workup, including upper and lower gastrointestinal screening and monitoring for other organ involvement, is essential in patients with elevated AEC counts and suspected HES or other eosinophilic disorders 1

From the Research

Clinical Significance of Absolute Eosinophil Count

The absolute eosinophil count (AEC) is a valuable diagnostic tool with various clinical applications. Some of the key uses of AEC include:

• Diagnosing and monitoring eosinophilic disorders, such as hypereosinophilic syndrome (HES) and chronic eosinophilic leukemia (CEL) 2, 3
• Identifying parasitic infections, such as those caused by helminthic parasites, which can lead to eosinophilia 4, 5
• Evaluating allergic reactions and autoimmune disorders, which can also cause elevated eosinophil levels 6, 5
• Assessing the presence of eosinophilic ascites, a condition characterized by elevated eosinophil counts in ascitic fluid 6
• Investigating infectious diseases in the head and neck region, such as allergic fungal rhinosinusitis and parasitic infections like toxocariasis and onchocerciasis 5

Diagnostic Thresholds

The diagnostic thresholds for eosinophilia vary depending on the condition being evaluated. For example:

• Eosinophilia is generally defined as an absolute count of > 500 eosinophils per mm3 of peripheral blood 4
• Hypereosinophilia is defined as a peripheral blood eosinophil count greater than 1.5 × 109 /L 2, 3

Clinical Applications

The AEC has several clinical applications, including:

• Monitoring disease progression and response to treatment in eosinophilic disorders 2, 3
• Guiding treatment decisions, such as the use of corticosteroids or immunomodulatory therapies 2, 3, 6
• Identifying potential complications, such as end-organ damage, in patients with eosinophilic disorders 2, 3