Excess inhaled corticosteroid adherence may be a marker of uncontrolled asthma

Background: The relationship between adherence to inhaled corticosteroids (ICS) in excess of 100% and asthma control is unclear. Methods: The Respiratory Effectiveness Group conducted a real-life study using a US healthcare database to examine the association between ICS medication possession ratio (MPR) >100% (a proxy measure of excess adherence) and asthma control. Eligible patients were 12–80 yrs and initiated ICS as hydrofluoroalkane beclometasone (n=2578) or fluticasone (n=7734). Over the one-year period following ICS initiation, MPR was calculated as the number of days’ supply of ICS/365 x 100% (categorized as ≤100%; >100%). Measures of asthma control consisted of severe exacerbations (unscheduled hospital admission or ER attendance for asthma or an acute course of oral corticosteroids) and Risk Domain Asthma Control (RDAC: no admission, ER attendance, or outpatient hospital attendance for asthma; no acute oral corticosteroids prescriptions; no consultation, hospital admission, or ER attendance for a lower respiratory tract infection requiring antibiotics, and no hospital admission or ER attendance for lower respiratory reasons) during the same period. Results: MPR>100% occurred in 7.2% of patients (n=742). Severe exacerbations were more common and RDAC attainment lower in patients with MPR >100% than in patients with MPR ≤100% (see table).   MPR≤100% MPR>100% p-value ≥1 exacerbation 25% 43% <0.001 ≥2 exacerbations 8% 21% <0.001 RDAC attainment 59% 40% <0.001 Conclusions: In clinical practice, adherence to ICS in excess of the label-defined dosing interval appears to be a marker of poorer asthma control. A MPR >100% may be a simple tool to identify patients in need of more intensive evaluation.