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.