Published Online: June 22, 2016
Airway hyperreactivity, which is determined by a positive bronchoprovocation challenge test, is a typical feature of bronchial asthma. Airway hyperreactivity may thus represent a subgroup of patients with chronic obstructive pulmonary disease (COPD) who have an “asthmatic" component. However, there are no diagnostic tools for identifying COPD patients with asthmatic features and little is known on how (or if) the asthmatic features modify patient-related outcomes in COPD.
In a recent research report in The Journal of Allergy and Clinical Immunology (JACI), Tkacova and colleagues evaluated the use of a methacholine challenge test as a possible diagnostic tool for identifying COPD patients with an asthmatic phenotype and determined the relationship of this phenotype to important clinical outcomes including patient symptoms, lung function decline, systemic inflammation and mortality using data from the Lung Health Study, which enrolled current smokers with mild-to-moderate COPD (5,887 patients). The results were then validated in a smaller study called GLUCOLD that enrolled former and current smokers with moderate-to-severe COPD (51 patients).
The researchers found that airway hyperreactivity was common affecting 1 in 4 patients with mild to moderate COPD. Patients with COPD who demonstrated airway hyperreactivity had more symptoms, experienced accelerated decline in their lung function, and death was two-fold higher from respiratory failure compared to patients without airway hyperreactivity. These relationships were present irrespective of COPD severity or smoking status. In contrast to airway hyperreactivity, bronchodilator reversibility, which has also been advocated as another objective measure of identifying COPD patients with asthmatic features, was not associated with increased risk of respiratory mortality.
Methacholine provocation testing is a powerful tool for identifying patients with COPD and these patients have increased risk of disease progression and respiratory mortality. Airway hyperreactivity may thus represent a spectrum of the asthma-COPD overlap phenotype that urgently requires disease modification. Importantly, results of the present study highlight the need of future interventional studies to modify respiratory mortality and decline in lung function in COPD patients with the asthma-COPD overlap phenotype.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.