Positive bronchial challenge test predicts asthma prevalence or risk in paediatric patients with atopic dermatitis

After evaluating a retrospective case series of paediatric patients with atopic dermatitis (AD), researchers from the Chinese University of Hong Kong (CUHK) found that a positive bronchial challenge test (BCT) result is independently and positively associated with personal history of asthma and sibling history of atopy, but not with any other clinical parameters.

“AD or eczema, asthma, and allergic rhinitis [AR] are associated diseases involved in the atopic march. Many children with AD develop asthma and/or AR when they reach adulthood,” wrote the researchers. [Pediatr Respirol Crit Care Med 2017;1:81-85; Iran J Allergy Asthma Immunol 2012;11:73-77] “Our study aimed to investigate whether personal characteristics, history of allergen exposure, skin prick test results, clinical assessment scores, laboratory parameters, and personal or family histories of atopic diseases are associated with a positive BCT result in paediatric AD patients, as findings would be useful in counselling parents and patients with AD on risks of asthma in the family.” [Hong Kong Med J 2021;27:27-34]

The BCT evaluates airway hyper-responsiveness to a low inhaled dose of methacholine and histamine in asthma patients, manifesting as acute contraction of bronchial smooth muscle lining, resulting in sudden narrowing and obstruction of the airway. This represents a type 1 hypersensitivity reaction mediated by immunoglobulin E (IgE), which is present in patients with hypersensitivity pneumonitis, asthma, and other atopic diseases. “IgE’s specific role in the induction of many allergic reactions is evidenced by its high serum level in patients with allergic and atopic diseases,” noted the researchers. [Molecules 2016;21:E753]

Of the 284 patients (age, >8 years) treated at the paediatric dermatology clinic of a university hospital from January 2000 to November 2017 with BCT results retrospectively selected for analysis, 106 had a positive result, while 178 had a negative result.

“A positive BCT result was associated with personal history of asthma [p<0.0005] and a sibling with asthma vs patients with a negative BCT result [28.6 percent vs 6.8 percent; p=0.048],” reported the researchers.

The adjusted odds ratio of a positive BCT result for asthma in patients with AD was 4.05, implying a four-fold greater likelihood of asthma vs BCT-negative AD patients. “This is consistent with the meta-analysis of 31 studies conducted in 102 countries, which found a 4.24 risk ratio of AD to AR and asthma. These results demonstrate a clear relationship between the skin and the airways,” commented the researchers. [PLoS One 2015;10:e0131869]

No significant associations were found between BCT results and personal AR, maternal atopy (specifically, asthma, AR, AD), paternal atopy (specifically asthma, AR, AD), siblings’ AR, and siblings’ AD. Moreover, BCT results were not associated with a history of skin prick response to allergens, including dust mites. “BCT may be of limited use in patients with AD beyond the prediction of asthma prevalence or risk,” concluded the researchers.

There are several contraindications for the BCT. “Patients with reduced lung function evidenced by baseline spirometry may be predisposed to a greater risk of serious adverse events. Individuals with a history of cardiovascular [CV] problems, increased intracranial pressure, or recent eye surgery may experience enhanced CV stress as a consequence of bronchoconstriction and should not be subjected to BCT,” pointed out the researchers. [Eur Respir J 2017;49:1601526; Am J Respir Crit Care Med 2000;161:309-329]