Although bronchial allergen challenge (BAC) is occasionally used to distinguish patients with allergic asthma among those with atopic asthma, it is currently considered a research tool without any protocols for use beyond diagnosing mild asthma and fulfilling study needs, according to Ioana Agache, MD, and colleagues.
Expanding Bronchial Allergen Challenge Application
A European Academy of Allergy and Clinical Immunology (EAACI) Task Force was assembled to address this limited use of BAC in AA diagnosis and care. According to the task force, “The correct diagnosis of AA might help select patients for immunomodulatory therapies. The clinical implementation of BAC could ultimately translate into better phenotyping of asthmatics in real life, and into a more accurate selection of patients for long-term and costly management pathways.”
For the position paper, Dr. Agache and team analyzed the literature on the topic and scrutinized the methodological aspects of BAC to determine its implementation into a protocol beyond occupational asthma. Some challenges that clinicians have noted in the application of BAC include the need for appropriate facilities with trained staff, long observation periods with the possibility of a late asthmatic response, and the allergens used eliciting more intense bronchoconstriction than other stimuli.
Path Toward Better Treatment
Recent advancements in the treatment of AA with allergen immunotherapy include sublingual tablets of house dust mite extract (HDM-SLT). However, this treatment requires distinguishing between AA and asthma with atopic sensitization, which makes BAC a necessary diagnostic tool.
The proposed methodology provided by the task force included recommendations for an appropriate clinical setting in which to perform BAC with the necessary equipment and trained staff. The test should be performed in the morning with the patient arriving 30 minutes before the test and refraining from strenuous activity. For pollen allergens, the test should be performed outside the pollination season.
A withdrawal period of 24-48 hours for inhaled corticosteroids (ICS) should be considered along with any other anti-inflammatory or anti-asthmatic drugs, according to Dr. Agache and colleagues. Allergen extracts that have been manufactured specifically for use in BAC should be applied whenever possible and those extracts manufactured for a skin prick test are not recommended for BAC.
Patients undergoing BAC should never be left unsupervised, and once an early asthmatic reaction is detected, the patient should be treated with salbutamol. Safety concerns were emphasized by the task force, as BAC can occasionally result in life-threatening bronchoconstriction. However, when properly performed, BAC can provide a more accurate characterization of asthma patients than currently used approaches alone, which can open the possibility of a more individualized and effective treatment regimen.