Is phenotype-based treatment practical?
This was studied in a proof-of-concept, randomized trial [24]. Sixty children aged 1-5 years with at least two wheeze attacks in the previous year were categorized on history as EVW or MTW. The intervention group was prescribed ICS if blood eosinophils ≥3%, or targeted antibiotics if there was a positive culture on induced sputum or cough swab, compared with a control group receiving standard care. The primary outcome was unscheduled health care visits over 4 months. There was no relationship between EVW, MTW and either blood eosinophils, atopic status or infection. Median blood eosinophils were 5.2 (range 0-21)%, 27 of 60 (45%) children were atopic, and 8 (13%) had airway bacterial infection. 67% in each group were prescribed ICS. There was no difference in the primary end point between groups. Median ICS adherence was 67% in the 50% of patients who returned adherence monitors. Also, parents were reluctant to change treatment during the winter viral season, when these patients were recruited; reluctance to change is also a feature of adult studies [57] and is a factor that needs to be overcome. In summary, clinical phenotype was unrelated to allergen sensitization or blood eosinophils. ICS treatment determined by blood eosinophils did not impact outcomes, but ICS adherence was poor.