In a 55-year-old man with a 20-year history of asthma now uncontrolled despite high-dose inhaled fluticasone‑salmeterol (Advair), tiotropium (Spiriva), and oral prednisone, with four exacerbations in the past year (one requiring hospitalization), marked eosinophilia (15% eosinophils, absolute count 1575), elevated total IgE (350 IU/mL), negative Aspergillus‑specific IgE, and normal nasal examination, which diagnostic test should be ordered next: stool ova‑and‑parasite studies, Aspergillus sputum culture, nasal endoscopy, or bronchoalveolar lavage?

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Last updated: September 27, 2026 • View editorial policy

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Order Stool Studies for Parasites

Given this patient's Southeast Asian origin, marked eosinophilia (absolute count 1575 cells/μL), and uncontrolled asthma despite maximal therapy, stool studies for ova and parasites should be ordered immediately to exclude parasitic infection as a treatable cause of his eosinophilia and refractory asthma.

Clinical Reasoning

This patient presents with several key features that demand systematic evaluation:

Why Not ABPA (Allergic Bronchopulmonary Aspergillosis)?

While the patient has significant eosinophilia (1575 cells/μL, exceeding the 500 cells/μL threshold) and elevated total IgE (350 IU/mL), ABPA is unlikely because:

  • Aspergillus-specific IgE is negative 1
  • Total IgE of 350 IU/mL falls below the diagnostic threshold of ≥500 IU/mL recommended by the 2024 ISHAM-ABPA guidelines 1
  • The 2024 guidelines explicitly state that sputum fungal culture has low sensitivity and specificity for diagnosing ABPA and is not recommended for this purpose 1

Therefore, Aspergillus sputum culture is not indicated at this time.

Why Not Nasal Endoscopy?

The patient has:

  • Normal nasal mucosa bilaterally on examination
  • No rhinorrhea, nasal congestion, or hearing changes
  • No clinical features suggesting allergic fungal sinusitis

Nasal endoscopy would not address the primary issue of marked peripheral eosinophilia and uncontrolled asthma 2.

Why Not Bronchoalveolar Lavage?

BAL is invasive and not indicated as a first-line diagnostic test when:

  • A simpler, non-invasive test (stool studies) can identify a highly treatable cause
  • There are no features suggesting invasive fungal disease or other conditions requiring BAL

The Critical Clue: Geographic Origin and Eosinophilia

Parasitic infection must be excluded in this patient because:

  1. Southeast Asian origin is a major risk factor for helminthic infections
  2. Marked eosinophilia (15%, absolute count 1575) significantly exceeds the threshold for type 2 inflammation 1
  3. Parasitic infections are a common and treatable cause of both eosinophilia and asthma exacerbations
  4. The eosinophilia is disproportionate to what would be expected from asthma alone

Differential Diagnosis of Eosinophilia

The 2024 ISHAM guidelines acknowledge that "eosinophilia may also be present in asthma, fungal-sensitised asthma and several other conditions" and that "overlap between different eosinophilia-associated diseases is frequent" 1.

Before attributing eosinophilia to severe asthma or considering expensive biologic therapy, parasitic infection must be ruled out.

Practical Algorithm

For this patient with uncontrolled asthma and marked eosinophilia:

  1. First: Order stool ova and parasites (×3 specimens on different days for optimal sensitivity)
  2. If negative: Consider CT chest to evaluate for bronchiectasis, mucus plugging, or high-attenuation mucus that might suggest ABPA despite negative Aspergillus-specific IgE
  3. If imaging unrevealing: Measure Aspergillus-specific IgG (the patient already has negative Aspergillus-specific IgE, but IgG ≥27 mgA/L would support ABPA) 1
  4. Only then: Consider more invasive testing or biologic therapy

Common Pitfalls to Avoid

  • Don't assume all eosinophilia in asthma is due to type 2 inflammation without excluding secondary causes
  • Don't pursue expensive or invasive testing before simple screening tests
  • Don't overlook geographic and epidemiologic risk factors that point to specific diagnoses
  • Don't rely solely on total IgE when it falls below diagnostic thresholds for ABPA 1

The patient's Southeast Asian origin combined with marked eosinophilia makes parasitic infection the most likely undiagnosed contributor to his refractory asthma, and this is easily assessed with stool studies.

References

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