Self-reported vs. objectively assessed adherence to inhaled corticosteroids in asthma

BACKGROUND: Adherence to inhaled corticosteroids (ICS) in asthma is vital for disease control. However, obtaining reliable and clinically useful measures of adherence remains a major challenge. We investigated the association between patient-reported adherence and objectively measured adherence based on filled prescriptions with inhaled corticosteroids in adults with asthma. METHODS: In total, 178 patients with asthma were asked to self-assess adherence during routine visits at a respiratory outpatient clinic. Self-assessment was performed using Foster score (“How many days in a 7-day week do you take your medication as prescribed?”, with the answer divided by 7). Objective adherence was calculated as medication possession ratio (MPR). Bivariate and multivariable linear regression, adjusted for age, sex, FEV(1), GINA treatment step, excessive use of SABA, and history of exacerbations were used for analyses. RESULTS: Of the included patients, 87.6% reported a Foster score of 100%, while the mean ICS MPR was 54.0% (SD 25%). Complex regimens such as twice-daily dosing or dual inhaler-use were associated with lower adherence (p = 0.015 and p < 0.001, respectively). Foster score was predictive of ICS MPR, with an absolute 32% increase in MPR between patients reporting Foster scores of 0 and 100% (95% CI 13–50%, p < 0.001). Female sex predicted higher ICS MPR (p = 0.019). Previous asthma-related hospitalization(s) predicted lower ICS MPR (p = 0.039). CONCLUSION: Although a weak association was found between Foster score and ICS MPR, findings do not support the use of Foster score, and by that self-reported adherence, as a reliable marker of controller adherence in asthma due to significant mismatch between patient-reported adherence and MPR. Future studies should address the complex interplay between patient-reported and objectively assessed adherence to controller medication in asthma. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40733-021-00072-2

Determining Persistence with an Inhaled Corticosteroid in Asthma:Assessment Using an Objective Measurement vs the Self-Reported Foster Score

INTRODUCTION: Adherence with controller medication is a major challenge in asthma management. Thus, a reliable method of measurement is mandatory to assess adherence. AIM: To examine the test-retest reliability on adherence with inhaled corticosteroids in adults with asthma using, a self-reported adherence score (Foster score). METHODS: Patients with asthma and >1 routine follow-up appointment at a university hospital outpatient clinic reported Foster scores. The objective Medication Possession Ratio (MPR) was calculated based on pharmacy redemption data and physician-prescribed doses of inhaled corticosteroids. The difference between Foster score and MPR at the first and second visit was assessed using a Bland–Altman plot, outcomes reported as limits of agreements and bias. Foster scores from both visits were used to calculate an intraclass correlation coefficient (ICC). RESULTS: Self-reported adherence with asthma controller medication measured by Foster score was significantly higher than the objective MPR (p < 0.0001). The Bland–Altman plot for MPR and Foster score at the first and second visit showed upper and lower limits of agreement of 83.5 – (−1.6) and 80.9 – (−6.9) and bias was 41.0 and 37.0, respectively. Of the included patients, 93.1% reported identical Foster scores between visits, resulting in an excellent ICC of 0.92. Absolute median difference between Foster scores and MPR at first and second visit was 8.7 percentage points (p = 0.049). CONCLUSION: Foster score shows an excellent ICC; however, its poor agreement with objective measures of adherence suggests that clinicians should not rely on Foster scores alone to assess adherence with inhaled corticosteroids in patients with asthma