Objective: To investigate true adherence with a dry powder inhaler, the Turbuhaler (TBH), in children with asthma. True adherence was calculated by multiplying adherence to treatment with inhaler competence, that is correct use of the inhaler.
Patients and design: In an 18-month study, children aged 5-10 years with asthma received twice daily budesonide via a TBH. Parents and children were trained in the correct use of the inhaler before the study started. For each inhalation, peak inspiratory flow through the TBH (PIF(TBH)) was recorded with an electronic pneumotachograph. The PIF(TBH) recordings were used to calculate true adherence for the first and last 45-day periods in the study by multiplying adherence in using the device (percentage of days with PIF(TBH) recordings) with inhaler competence (correct use of inhaler defined as PIF(TBH) values >40 l/min).
Main outcome measures: True adherence, adherence, inhaler competence and PIF(TBH).
Results: 115 children were treated. The mean (morning and evening) true adherence during the first 45 days was 81.6% (range 78.1-86.4%) and during the last 45 days 57.4% (44.0-66.9%). Mean adherence was 86.0% and 59.3%, whereas mean inhaler competence was 94.7% and 96.2%, respectively. Thus the decline in true adherence was due to the decline in adherence. The largest decline in true adherence occurred in older children.
Conclusions: True adherence with budesonide TBH treatment decreased significantly during the 18-month study due to a decrease in adherence. Inhaler competence with the correct use of the budesonide TBH was high and unchanged over the study period.