Diagnostic Criteria and Management of Allergic Bronchopulmonary Aspergillosis (ABPA)

Introduction to ABPA Diagnostic Criteria

The 2024 revised ISHAM-ABPA working group consensus criteria require predisposing conditions or compatible clinical presentation, plus two essential components (A. fumigatus-specific IgE ≥0.35 kUA·L−1 and serum total IgE ≥500 IU·mL−1), along with any two additional components from the criteria, for diagnosing ABPA 1, 2
Predisposing conditions for ABPA include asthma, cystic fibrosis, COPD, and bronchiectasis, or compatible clinico-radiological presentation 1, 2

Essential components for ABPA diagnosis include A. fumigatus-specific IgE ≥0.35 kUA·L−1 1, 2
Serum total IgE ≥500 IU·mL−1 is another essential component for ABPA diagnosis 1, 2
Other components that can support ABPA diagnosis include positive IgG against A. fumigatus, blood eosinophil count ≥500 cells·μL−1, and thin-section chest CT consistent with ABPA or fleeting opacities on chest radiograph 1, 2

The 2024 guidelines establish separate criteria for ABPM caused by fungi other than Aspergillus fumigatus, including elevated fungus-specific IgE and serum total IgE ≥500 IU·mL−1 2, 4
Other components for ABPM diagnosis include positive fungus-specific IgG, blood eosinophil count ≥500 cells·μL−1, and two sputum or one BAL fluid culture growing the causative fungus 4

The 2024 guidelines provide a clinical classification system for ABPA, including acute ABPA, response, remission, treatment-dependent ABPA, and advanced ABPA 5, 6
Acute ABPA is defined as newly diagnosed ABPA meeting diagnostic criteria, while exacerbation is defined as clinical/radiological worsening with ≥50% increase in serum total IgE 5, 6

The 2024 guidelines classify ABPA radiologically into five categories, including ABPA-S, ABPA-B, ABPA-MP, ABPA-HAM, and ABPA-CPF 7, 8
ABPA-S is defined as serological ABPA without bronchiectasis, while ABPA-B is defined as ABPA with bronchiectasis 7

Oral prednisolone (0.5 mg·kg−1·day−1 for 2-4 weeks, tapered and completed over 4 months) is recommended as first-line treatment for acute ABPA 8
Antifungal azoles, particularly itraconazole, can be used as alternative or adjunctive treatments for treatment-dependent ABPA or as steroid-sparing agents 8

High-attenuation mucus is pathognomonic of ABPA and confirms diagnosis even if other criteria are not fulfilled 1, 2
A positive type 1 skin test is acceptable when Aspergillus-IgE testing is unavailable 2
Serum total IgE <500 IU·mL−1 may be acceptable if all other criteria are fulfilled 2, 3
Elevated IgE against rAsp f1, f2, and f4 supports the diagnosis and can be used as another diagnostic component 2
Caution is advised when combining methylprednisolone with oral itraconazole due to higher risk of exogenous Cushing's syndrome and adrenal insufficiency 8