In an otherwise healthy adult with an absolute eosinophil count of 871 cells/µL, what is the appropriate diagnostic work‑up and initial management?

Evaluation of Absolute Eosinophil Count of 871 cells/µL

An absolute eosinophil count of 871 cells/µL represents mild eosinophilia that warrants systematic evaluation focused on allergic disorders and parasitic infections, with the specific workup determined by travel history, atopic symptoms, and gastrointestinal manifestations. 1

Initial Risk Stratification

Your eosinophil count falls into the mild eosinophilia category (500–1,500 cells/µL), which carries significantly lower risk than moderate-to-severe elevations. 1, 2 At this level:

• Allergic disorders account for the majority of cases in patients without travel to endemic regions (approximately 50–80% have concurrent atopic conditions such as allergic rhinitis, asthma, or atopic dermatitis). 1
• In patients with travel history to tropical or subtropical regions, helminth infections explain 19–80% of mild eosinophilia cases. 1
• Allergy alone rarely produces counts above 1,500 cells/µL, so your level is consistent with common secondary causes rather than primary hematologic disorders. 1

Essential History Elements

Travel and Exposure Assessment

• Document any travel to helminth-endemic areas (tropical/subtropical regions), particularly noting fresh water exposure in Africa, consumption of raw or undercooked meat, and the timing relative to eosinophilia onset. 1
• Even remote travel history is relevant because Strongyloides can persist lifelong and cause fatal hyperinfection syndrome in immunocompromised hosts. 1

Symptom-Directed Inquiry

• Screen for dysphagia or food impaction, which would mandate endoscopic evaluation for eosinophilic esophagitis. 1
• Assess for respiratory symptoms (persistent cough, wheezing, dyspnea) that might indicate pulmonary eosinophilic disease. 1
• Review all current and recent medications, as pharmaceutical agents are a frequent trigger of eosinophilia. 1
• Evaluate for atopic manifestations including allergic rhinitis, asthma, atopic dermatitis, and seasonal symptom patterns. 1

Recommended Diagnostic Workup

For Patients WITH Travel History to Endemic Regions

Parasitic evaluation is mandatory regardless of symptoms: 1

• Three separate concentrated stool specimens for ova and parasites 1
• Strongyloides serology and culture 1
• Schistosomiasis serology if fresh water exposure occurred in endemic areas 1

Critical caveat: Many helminth-infected patients do not have eosinophilia, so normal counts do not exclude infection; conversely, eosinophilia alone is not adequate screening. 1

For Patients WITHOUT Travel History

Focus on allergic and medication-related causes: 1

• Comprehensive medication review, specifically noting nitrofurantoin and other common culprits 1
• Aeroallergen sensitivity testing (skin-prick or specific IgE) to identify trigger allergens in patients with atopic symptoms 1
• Consider seasonal pollen exposure as a contributor, particularly during spring/summer months 1

For Patients WITH Gastrointestinal Symptoms

Endoscopic evaluation is required when dysphagia or food impaction is present: 3

• Upper endoscopy with at least six biopsies (2–3 from proximal and 2–3 from distal esophagus) 3, 1
• Diagnostic threshold is ≥15 eosinophils per 0.3 mm² (high-power field) in any biopsy specimen 3
• Important: Peripheral eosinophilia occurs in only 10–50% of adults with eosinophilic esophagitis, so normal blood counts do not exclude the diagnosis. 1, 4

Initial Management Approach

Watch-and-Wait Strategy

For mild eosinophilia without organ involvement or travel history, regular monitoring every 3–6 months is appropriate after addressing secondary causes. 1 This includes:

• Optimizing control of co-existing atopic diseases (asthma, allergic rhinitis, eczema) 4
• Discontinuing potentially causative medications when feasible 1
• Implementing aeroallergen avoidance strategies during peak pollen seasons 1

When to Escalate Evaluation

Referral to hematology is required if: 1

• Eosinophilia persists >3 months after infectious causes have been excluded or treated 1
• Count rises to ≥1,500 cells/µL on repeat testing 1
• Any symptoms suggesting end-organ damage develop (cardiac, pulmonary, neurologic) 1

Common Pitfalls to Avoid

• Do not assume eosinophilia alone screens adequately for helminth infection; many infected patients have normal counts. 1
• Do not rely solely on peripheral eosinophil counts to diagnose eosinophilic esophagitis; tissue biopsy is the gold standard. 1, 4
• Do not overlook medication review; pharmaceutical agents are frequently implicated. 1
• Do not dismiss the importance of seasonal variation; pollen exposure can modulate eosinophil levels in atopic individuals. 1
• Do not use diethylcarbamazine if Loa loa microfilariae are present on blood film, as it may cause fatal encephalopathy. 1

Monitoring Plan

If initial workup is unrevealing and count remains stable: 1

• Repeat absolute eosinophil count every 3–6 months 1
• Reassess atopic disease control and environmental exposures at each visit 1
• Re-evaluate if count rises, symptoms develop, or new exposures occur 1