Managing recurrent wheezing in preschool children is problematic, with conflicting evidence on the effectiveness of asthma therapy. One reason is the heterogeneous nature of preschool wheeze: distinguishing “transient viral wheeze” from asthma at presentation is currently impossible. Bronchodilator response (BDR) measured by interrupter resistance (Rint) is greater in preschool children with diagnosed asthma than in healthy controls, but the usefulness of Rint in clinical practice has not been studied. We aimed to assess whether measuring BDR using Rint can predict clinical response to inhaled corticosteroids (ICS).

We studied children aged 2 years to 1. Response to ICS was defined as reduction in daily symptom score of at least 0.26.² Association between BDR and ICS response was assessed using chi-square test. We also assessed the relationship between measured BDR and the caregiver’s assessment.

121 children were recruited, 59 completed the full study (27 withdrew, 10 were unable to perform Rint, 18 failed to meet 4w symptom threshold, 7 commenced ICS or Montelukast by clinician before 4w). Positive BDR at baseline was demonstrated by 33 children, and was significantly associated with a clinical response to ICS (p < 0.05). There was no relationship between objective BDR and caregiver’s rating of bronchodilator efficacy.

Our findings suggest that measuring BDR using Rint may help in making pragmatic decisions on commencing asthma preventer therapy in wheezy preschool children. Further work is needed to assess whether Rint BDR measurement may have the potential to distinguish those with transient wheeze from those with asthma.

References 1 Pediatr. Pulmonol. 2010;45:633–638

2 Pediatrics 2001;108:E48