Investigations

The investigation of allergic bronchopulmonary aspergillosis should include the following: (1)

• chest X-ray; shows various transient abnormalities:
  • consolidation or collapse
  • thickened bronchial wall markings
  • peripheral shadows
  • signs of proximal bronchiectasis
    
• full blood count; reveals eosinophilia. (A total eosinophil count of over 500 is one of the diagnostic criteria for ABPA in patients with asthma). (2)
  
• serum IgE levels will be raised and precipitating antibodies to Aspergillus species present in 90% of cases. Note - the combination of elevated total serum IgE and elevated specific IgE to recombinant Aspergillus allergen f4 and/or recombinant Aspergillus allergen f6 allows classic ABPA to be diagnosed with 100% specificity and 64% sensitivity, and with a 100% positive predictive value and 94% negative predictive value. (3)
  
• fungal spores or hyphae may be seen on sputum microscopy or grown on culture
  
• skin-prick test; the sensitivity of Aspergillus skin testing for ABPA is very high (>95% in prior studies), but the specificity is relatively low. Only 25% to 37% of patients with a positive Aspergillus skin test end up meeting the full criteria for ABPA. (4)

• high-resolution CT of the chest; might be ordered to assess for characteristic radiographic findings of ABPA. (5) This can show up high-attenuation mucus (mucus which is visually denser than paraspinal skeletal muscle) and which is considered the closest things to a pathognomonic sign for ABPA, with 100% specificity. When present at the time of diagnosis it also predicts poor outcomes. (6)

References

1. Patterson TF et al. Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2016 Aug 15;63(4):e1-e60
2. Agarwal R, Saxena P, Muthu V, et al. Evaluation of simpler criteria for diagnosing allergic bronchopulmonary aspergillosis complicating asthma. Front Cell Infect Microbiol. 2022;12:861866.
3. Casaulta C, Fluckiger S, Crameri R, et al. Time course of antibody response to recombinant Aspergillus fumigatus antigens in cystic fibrosis with and without ABPA. Pediatr Allergy Immunol. 2005;16:217-225.
4. Shah A, Panjabi C. Allergic aspergillosis of the respiratory tract. Eur Respir Rev. 2014 Mar 1;23(131):8-29.
5. Agarwal R, Chakrabarti A, Shah A, et al. Allergic bronchopulmonary aspergillosis: review of literature and proposal of new diagnostic and classification criteria. Clin Exp Allergy. 2013 Aug;43(8):850-73.
6. Agarwal R, Maskey D, Aggarwal AN, et al. Diagnostic performance of various tests and criteria employed in allergic bronchopulmonary aspergillosis: a latent class analysis. PLoS One. 2013;8(4):e61105.