Joannie Shen; Michael Johnston; Ron D Hays


Expert Rev Pharmacoeconomics Outcomes Res. 2011;11(4):447-453. 

In This Article

Airway Hyper-responsiveness

Airway hyper-responsiveness is a measure of variable airflow limitation and is one of the defining features of asthma. AHR reflects the increased sensitivity of the airways to inhaled stimuli, even when spirometric results are normal. AHR is commonly measured by using direct or indirect challenge tests (referring to the mode of action of the agents in relation to smooth-muscle contraction; methacholine is commonly used as a direct smooth-muscle stimuli). AHR is a crucial outcome measure in studies focusing on modifying underlying disease activity. Direct challenge agents can be considered for assessing mid- and long-term disease modification, while indirect challenge agents are relatively more responsive when investigating short-term responses to anti-inflammatory interventions.

Airway hyper-responsiveness is only weakly associated with symptoms, lung function and markers of airway inflammation,[53] but provides independent and complementary information.[54] Studies performed with direct-challenge agents have demonstrated that AHR is strongly related to the clinical course of asthma. Increased AHR is an important risk factor: it predicts loss of control of asthma[55,56] and development of irreversible loss of lung function.[57,58] Increased AHR is a significant risk factor for the subsequent development of physician-diagnosed asthma and chronic obstructive pulmonary disorder in the general population.[59]

Airway hyper-responsiveness is considered an integrative disease marker reflecting multiple pathophysiological mechanisms and should be included in asthma therapeutic trials. In treatment, AHR-guided therapy has shown promise in preventing lung-function decline[60,61] by targeting bronchial hyper-responsiveness.[62]


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