Clinical judgment is required because signs and symptoms vary widely from patient to patient as well as within each patient over time.
Airflow obstruction is at least partially reversible.
Alternative diagnoses are excluded. This section differs from the 1991 Expert Panel Report in several ways. Asthma severity classifications have been changed from mild, moderate, and severe to mild intermittent, mild persistent, moderate persistent, and severe persistent to more accurately reflect the clinical manifestations of asthma. The Panel emphasizes that patients at any level of severity can have mild, moderate, or severe exacerbations. In addition, information on wheezing in infancy and vocal cord dysfunction has been expanded in the differential diagnosis section in component 1.