What is the recommended evaluation and management approach for Allergic Bronchopulmonary Aspergillosis (ABPA)?

ABPA Evaluation: A Structured Diagnostic Approach

All newly diagnosed asthmatic adults in tertiary care settings should be screened for Aspergillus fumigatus sensitization using A. fumigatus-specific IgE (cut-off ≥0.35 kUA·L⁻¹), as this is the preferred initial screening test with 99-100% sensitivity. 1

Initial Screening Strategy

Who to Screen

• Adults with asthma: All newly diagnosed asthmatic adults seeking tertiary care require screening for A. fumigatus sensitization, as ABPA can occur even in mild asthmatics and carries high risk of progression to bronchiectasis if undetected 1
• Children with asthma: Screen only those with difficult-to-treat asthma, not all asthmatic children 1
• Re-evaluation: Consider re-screening in patients with previously negative A. fumigatus-specific IgE if there is unexplained deterioration in asthma control 1

Preferred Screening Test

• A. fumigatus-specific IgE is superior to skin prick testing (sensitivity 99-100% vs 88-94%) and should be the first-line screening tool 1
• Skin prick test may be performed additionally or when fungus-specific IgE is unavailable 1
• A. fumigatus-IgE can also detect sensitization to other Aspergillus species, particularly A. flavus 1
• Assessment for other fungi (Candida, Penicillium, Alternaria, Cladosporium, Trichophyton) should be reserved for difficult-to-treat asthmatic patients with negative A. fumigatus sensitization 1

Diagnostic Workup for Sensitized Patients

Once A. fumigatus sensitization is confirmed, perform the following immunological panel to exclude ABPA:

Essential Laboratory Tests

• Serum total IgE: Use cut-off ≥500 IU·mL⁻¹ (by enzyme immunoassay) for ABPA diagnosis—this represents a critical update from the previous ≥1000 IU·mL⁻¹ threshold, offering higher sensitivity (98% vs 91%) 1
• A. fumigatus-specific IgG: Use population-specific cut-offs when available; otherwise use manufacturer-recommended values (noting these vary: India ≥27 mgA·L⁻¹, Japan ≥60 mgA·L⁻¹, UK ≥40 mgA·L⁻¹) 1
• Peripheral blood eosinophil count: Use cut-off ≥500 cells·μL⁻¹ for ABPA diagnosis 1
• A. fumigatus-specific IgE: Quantitative measurement 1

Tests NOT Recommended

• Serum galactomannan: Do not use for diagnosing ABPA 1
• Aspergillus skin test and serum precipitins: No consensus reached for routine recommendation due to variable access and diagnostic accuracy, though may be used when automated immunoassays are unavailable 1

Microbiological Evaluation

• Sputum fungal culture: Suggested during ABPA evaluation to identify species and guide therapy 1
• Sputum fungal culture is mandatory for evaluating allergic bronchopulmonary mycosis (ABPM) caused by non-Aspergillus fungi 1

Radiological Assessment

Baseline Imaging

• Thin-section chest CT is essential at baseline to identify and characterize bronchiectasis, mucus plugging, high-attenuation mucus (HAM), and other abnormalities in suspected ABPA 1
• Chest CT provides critical information for classification (ABPA with bronchiectasis vs ABPA without bronchiectasis), assessment of disease extent, and prognostication 1

Follow-up Imaging

• Use chest radiograph (not CT) for monitoring treatment response to minimize radiation exposure 1
• Assess response at 8-12 weeks using clinical symptoms, serum total IgE levels, and chest radiographs 2

Role of Bronchoscopy

Bronchoscopy is NOT routinely recommended for diagnosing ABPA 1

Limited Indications for Bronchoscopy

Perform bronchoscopy only in these specific situations: 1

• Uncertain diagnosis requiring respiratory samples for fungal culture
• Suspected ABPM where sputum cultures are uninformative or cannot be obtained
• Unexplained hemoptysis
• Suspicion of chronic infection (tuberculous or non-tuberculous mycobacterial) before initiating systemic glucocorticoids
• Therapeutic need to remove mucus plugs causing respiratory failure or recalcitrant to systemic therapy 1

Monitoring During Treatment

Response Assessment (8-12 weeks)

Good response is defined as: 2

• ≥50% improvement in symptoms (Likert scale)
• Improvement on chest imaging
• ≥20% reduction in serum total IgE levels

Long-term Monitoring

• First year: Clinical review, serum total IgE, and lung function tests every 3-6 months 2
• Subsequent years: Every 6-12 months 2
• "New baseline" IgE: The last recorded serum total IgE during clinical stability becomes the reference point 1

Exacerbation Detection

ABPA exacerbation is defined as: 2

• Sustained worsening of clinical symptoms (≥2 weeks) OR new infiltrates on chest imaging
• AND increase in serum total IgE by ≥50% above the "new baseline" 1, 2
• Note: Total IgE is far more useful than A. fumigatus-specific IgE for monitoring, as specific IgE may increase in 52% of patients even during treatment response and rises in only 38.5% during exacerbations 3

Critical Pitfalls to Avoid

• Do not use the outdated total IgE cut-off of ≥1000 IU·mL⁻¹—the revised threshold of ≥500 IU·mL⁻¹ significantly improves sensitivity 1
• Do not rely on A. fumigatus-specific IgE for monitoring treatment response—it has limited utility and may paradoxically increase during successful treatment 3
• Do not perform routine bronchoscopy—it is invasive and rarely changes management unless specific indications are present 1
• Do not use chest CT for routine follow-up—chest radiograph is adequate and reduces radiation exposure 1
• Be aware that cut-off values for A. fumigatus-specific IgG vary by population and assay method—use locally validated thresholds when available 1