Classification of asthma.

Asthma is a chronic inflammatory disorder of the airways that results, 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. Asthma can be classified 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 (immunoglobulin E mediated), nonallergic (often triggered by viral upper respiratory tract infections or no apparent cause), occupational, aspirin-exacerbated respiratory disease, potentially 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, or beta₂-adrenergic agonists, and to treatment for acid reflux and rhinosinusitis. Thus, cough variant asthma is in the differential diagnosis of chronic cough.