Adherence to inhalers in patients with severe asthma treated with anti-interleukin-5 biologics

Abstract

Objective: Given poor medication adherence in severe asthma is difficult to evaluate in daily practice, using at least two methods concurrently is recommended. We aimed to determine the prevalence of nonadherence to inhalers using the Test of Adherence to Inhalers questionnaire and the medication possession ratio obtained from the pharmacy refill data in patients with severe asthma treated with anti-interleukin-5 biologics and to evaluate their concordance. Method: This was a cross-sectional retrospective observational study of 53 patients with severe asthma recruited from the severe asthma unit of a tertiary hospital in Madrid from June to December 2020. We registered demographic data, comorbidities and concomitant therapy for asthma. Nonadherence was defined as pharmacy refill data < 80% and/or Test of Adherence to Inhalers questionnaire results < 50. Concordance was assessed by determining the Cohen's kappa statistic. Results: The median age was 61 years (interquartile range 51.8-67.0), and 33 (61%) were women. According to the pharmacy refill data lack of adherence to the primary inhaler was 58.5%. However, when using the Test of Adherence to Inhalers questionnaire, it was 22.6%. Combining both methods, 17% of patients were considered to have nonadherence to inhalers. Likewise, when identifying nonadherence by either of these methods, it reached a prevalence of 64.2%. The pharmacy refill data and Test of Adherence to Inhalers questionnaire agreed in 53.1% and disagreed in 46.9% of patients (k = 0.137; 95% confidence interval -0.057 to 0.331; p = 0.318). Conclusions: We observed a higher prevalence of non-adherence to inhalers in patients with severe asthma treated with anti-interleukin-5 biologics. The agreement between the Test of Adherence to Inhalers questionnaire and the pharmacy refill data is lower when evaluating nonadherence in patients with severe asthma treated with anti-interleukin-5 biologics. The pharmacy refill data detect a higher proportion of nonadherence compared with the Test of Adherence to Inhalers questionnaire.