Allergic Bronchopulmonary Aspergillosis (ABPA)

At a Glance

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity disorder that occurs in immunocompetent individuals (typically children and young adults) exposed to inhaled Aspergillus spores. Most patients have underlying asthma or cystic fibrosis. ABPA should not be confused with invasive aspergillosis, a life-threatening disease of immunocompromised patients or aspergillomas (fungus balls) that can form in previously damaged lungs (e.g., within parenchymal cysts or bronchiectatic airways). Hypersensitivity to Aspergillus occurs when a susceptible individual inhales spores that produce hyphae within the bronchial mucus and induce a Th2 CD4 T lymphocyte-mediated response. Roles for mucus quality and pre-existing bronchial epithelial activation have been suggested.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

It is uncommon for ABPA to occur in patients without underlying asthma or cystic fibrosis. Most asthmatic patients who develop ABPA also exhibit other signs of atopy (e.g., atopic dermatitis, rhinitis, conjunctivitis, and sensitization to other aeroallergens). Although there is no definitive set of laboratory abnormalities that are diagnostic in ABPA, the following findings are supportive: peripheral blood eosinophilia, elevated serum total IgE concentration (>1000 ng/ml), elevated Aspergillus fumigatus-specific serum IgE concentration, and precipitating serum antibodies to Aspergillus fumigatus.

Patients with ABPA may be skin test-positive to challenge with Aspergillus antigens, but patients without ABPA may also be positive. Other helpful, but less specific, findings include mucous plugs that contain eosinophils, Charcot-Leyden crystals, and Aspergillus hyphae or hyphal fragments.

Serum total IgE concentrations are helpful in monitoring response to therapy. IgE concentrations tend to peak during acute or exacerbation phases of ABPA and then decrease over a period of 6-8 weeks. Patients with ABPA who develop bronchiectasis and pulmonary fibrosis suffer from pulmonary complications similar to those seen in cystic fibrosis, that is, bronchial colonization by Staphylococcus aureus and/or Pseudomonas aeruginosa.

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?

Aspergillus antigens is the most common cause of ABPA, but other species (e.g., A flavus, A niger, A nidulans) of Aspergillus have been associated with this clinical syndrome. Also, other fungi can cause a similar clinical syndrome. The list of reported organisms is long but includes Candida, Helminthosporium, Stemphylium, as well as others. As noted previously, treatment with corticosteroids may reduce IgE concentrations and, thus, interfere with diagnostic testing.

What Lab Results Are Absolutely Confirmatory?

There is no single confirmatory laboratory test. In the appropriate clinical setting, absolute eosinophil count, total serum IgE, serum Aspergillus fumigatus IgE antibody, and serum Aspergillus fumigatus precipitating antibody measurements are useful.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Patients with chronic obstructive pulmonary disease (other than asthma), hyper-IgE syndrome, chronic granulomatous disease, and bronchocentric granulomatous disease along with APBA have been reported. Thus, clinical setting and signs and symptoms of bronchial disease (i.e., cough, wheezes, sputum production, exercise intolerance) are important.