Chapter 9: Asthma classification

Asthma is a chronic inflammatory disorder of the airways resulting physiologically in hyperreactivity and clinically in recurrent episodes of wheezing, chest tightness, or coughing. Airway inflammation, smooth muscle contraction, epithelial sloughing, mucous hypersecretion, bronchial hyperresponsiveness, and mucosal edema contribute to the underlying pathophysiology of asthma. Diagnostic tests such as methacholine or mannitol challenges or spirometry (pre- and postbronchodilator responses) help to identify such underlying pathophysiology via assessments of bronchial hyperreactivity and lung mechanics but are imperfect and ultimately must be viewed in the context of a patient's clinical presentation including response to pharmacotherapy. The National Asthma Education and Prevention Program Expert Panel Report (2007) classifies asthma into either intermittent or persistent, and the latter is either mild, moderate, or severe. Some patients change in either direction from intermittent to persistent asthma. In addition, patients with asthma may be classified as allergic (IgE mediated), nonallergic (often triggered by viral upper respiratory tract infections or no apparent cause), occupational, aspirin-exacerbated respiratory disease, potentially (near) fatal, exercise induced, and cough variant asthma. In the latter, the patients have a nonproductive cough that responds to treatment for asthma but not with antibiotics, expectorants, mucolytics, antitussives, beta2-adrenergic agonists, treatment for acid reflux, or rhinosinusitis. Thus, cough variant asthma is in the differential diagnosis of chronic cough.