17th January 2024

Diagnosis

ABPA should be suspected in any patient with CF or asthma presenting with several exacerbations, upper zone bronchiectasis, eosinophilia and raised IgE. It is rare to develop the condition without the underlying disease of CF or asthma. A number of investigations are needed to rule in or out a diagnosis of ABPA as follows:

1. Bloods
   • Eosinophilia – can be seen in blood tests and histology results. May be absent if steroids are taken regularly.
   • Total serum IgE – also usually raised in ABPA
   • Specific serum IgE and IgG to Aspergillus fumigatus may also be raised
2. Imaging
   • A chest X-ray will likely show non-specific features, and if ABPA is suspected, CT imaging should be performed.
   • HRCT of the chest can show bronchiectasis (mainly in the central lobes), mucus plugging, centrilobular nodules and bronchial wall thickening and dilatation.
3. Other investigations
   • Sputum culture – may be positive for presence of Aspergillus fumigatus but can also show no growth.
   • Skin test – to establish if an individual is sensitised to the fungus (type 1 hypersensitivity reaction occurs if so).
   • HLA-DR molecules – this gene marker is associated with ABPA, but it is not a routine clinical test.
   • Lung function tests – in ABPA, an obstructive pattern is usually seen, with reduced FEV1 and increased residual volume. However, fibrosis and/or bronchiectasis can cause a mixed or restrictive pattern to occur as well.