Figure 1.

A large subgroup of patients has persistent absence of eosinophils in their airways. Two to four measures of eosinophil percentage in induced sputum from subjects with asthma were made over a period as long as 1 year. The subjects with asthma were not taking inhaled corticosteroids for disease management. The graph reveals three subgroups of subjects with asthma: (1) those with persistently eosinophilic asthma whose sputum eosinophil percentage is greater than or equal to 2% on every occasion it was measured; (2) those with intermittently eosinophilic asthma whose sputum eosinophil percentage is greater than 2% on at least one occasion but can be less than 2% on some occasions; and (3) a third subgroup whose sputum eosinophil percentage is persistently less than 2% on all occasions measured. Note that the number of subjects varies at each time point. Reproduced by permission from Reference 6.