From the Guidelines
High IgE levels, eosinophilia, and positive IgG Aspergillus serology together suggest allergic bronchopulmonary aspergillosis (ABPA), a hypersensitivity reaction to Aspergillus fungi in the airways, as indicated by the revised ISHAM-ABPA working group clinical practice guidelines 1. This condition typically occurs in patients with asthma or cystic fibrosis. The elevated IgE indicates an allergic response, while eosinophilia (increased eosinophils in the blood) reflects allergic inflammation. Positive IgG Aspergillus serology shows previous exposure to the fungus. The diagnosis of ABPA requires a combination of clinical, immunological, and radiological findings, including:
- Predisposing conditions such as asthma or cystic fibrosis
- Essential components:
- A. fumigatus-specific IgE ≥0.35 kUA·L−1
- Serum total IgE ≥500 IU·mL−1
- Other components (any two):
- Positive IgG against A. fumigatus
- Blood eosinophil count ≥500 cells·μL−1
- Thin-section chest computed tomography consistent with ABPA (bronchiectasis, mucus plugging, and high-attenuation mucus) or fleeting opacities on chest radiograph consistent with ABPA Treatment usually involves oral corticosteroids (such as prednisone 0.5 mg/kg/day for 2 weeks, then tapered over 2-3 months) to reduce inflammation, and antifungal medications like itraconazole (200 mg twice daily for 16-24 weeks) to decrease fungal burden, as recommended by the guidelines 1. Patients should also optimize management of any underlying conditions like asthma. This combination of findings requires further clinical correlation including chest imaging (to look for bronchiectasis or infiltrates) and pulmonary function tests. The condition can lead to permanent lung damage if left untreated, so prompt evaluation by a pulmonologist or allergist is recommended, as emphasized by the British Thoracic Society guideline for bronchiectasis in adults 1.
From the Research
Interpretation of Test Results
- High IgE levels, eosinophilia, and positive IgG Aspergillus serology can be indicative of Allergic Bronchopulmonary Aspergillosis (ABPA) 2, 3, 4.
- ABPA is a pulmonary disorder that results from a hypersensitivity reaction to the fungi Aspergillus fumigatus, and it presents with pulmonary infiltrates and bronchiectasis 2.
- The combination of high total IgE, A. fumigatus-specific IgE, and total eosinophil count can be used to differentiate ABPA from asthma, with cut-off values of 2347 IU ml(-1), 1.91 kUA l(-1), and 507 cells per μl respectively 4.
- The sensitivity and specificity of these parameters are 87/81%, 99/87%, and 79/76% respectively, with the combination of these three tests providing 100% specificity 4.
- Aspergillus fumigatus-specific IgG can be a useful test in the diagnosis and differential diagnosis of ABPA, but it is unreliable in monitoring treatment response in this disorder 3.
Diagnostic Considerations
- The diagnosis of ABPA should be considered in patients with asthma and high IgE levels, eosinophilia, and positive IgG Aspergillus serology 2, 3, 4.
- The cut-off values of immunological tests employed in the diagnosis of ABPA should be validated, and further studies from different centers are required to confirm these values 4.
- The treatment of ABPA should be guided by evidence-based protocols, and larger clinical trials are needed to establish more formal treatment protocols for ABPA 2.