Accuracy of patient self-report as a measure of inhaled asthma medication use

Background and objective: Measuring adherence to inhaled asthma treatment is a key priority for asthma care. The aim of this study was to determine the relationship between self-report and actual medication use as measured by electronic monitoring for single and combination inhaled corticosteroid (ICS) and long-acting beta-agonist (LABA) metered-dose inhaler therapy.

Methods: In this retrospective analysis from a previously completed prospective 24-week randomized, controlled trial of single or combination ICS/LABA therapy, medication use in the week prior to study visits determined by self-report questionnaire and electronic monitoring was compared. One hundred eleven participants received 125 µg fluticasone dipropionate and 25 µg salmeterol, two actuations twice daily, by either separate or combination ICS/LABA inhalers. Paired data for self-report and electronic monitoring were analysed. Measurement of agreement was by Bland-Altman-like plots by visit with calculation of limits of agreement.

Results: For single and combination ICS/LABA therapy, self-report consistently overestimated actual inhaler use assessed by electronic monitoring by a mean of 2.2-8.4 inhalations over a 1-week period, with limits of agreement ranging from ±15.8 to 25.6 inhalations. Participants who underused their inhalers tended to overreport their use, while those who overused tended to underreport their medication use. The greater the degree of underuse, the greater the magnitude of overreport, and likewise, the greater the degree of overuse, the greater the magnitude of underreport.

Conclusions: Self-report is inaccurate in measuring actual use of inhaled asthma treatment with patients who underuse their maintenance therapy overreporting their use and those who overuse their therapy underreporting their use.