Background: Adherence to inhaled corticosteroids (ICSs) is known to be poor among patients with asthma; however, little is known about patients who do not fill their ICS prescriptions (ie, primary nonadherence).
Objective: To estimate rates of primary nonadherence and to explore associated factors.
Methods: The study population was members of a large health maintenance organization in southeast Michigan who met the following criteria: age 5 to 56 years; previous diagnosis of asthma; at least 1 electronic prescription for an ICS between February 17, 2005, and June 1, 2006; and at least 3 months follow-up after the ICS prescription. Adherence was estimated by using electronic prescription information and pharmacy claims data. Multivariable stepwise analysis was used to identify factors associated with primary nonadherence compared with adherent patients.
Results: One thousand sixty-four patients met the study criteria and had calculable adherence. Of these patients, 82 (8%) never filled their ICS prescription. Stepwise regression identified the following factors to be associated with an increased likelihood of primary nonadherence: younger age, female sex, African American race-ethnicity, and lower rescue medication use. Factors associated with primary nonadherence differed between race-ethnic groups.
Conclusion: Primary nonadherence was associated with lower baseline rescue medication use, which may reflect lower perceived need for ICS therapy in patients with milder asthma. Rates of primary nonadherence and the factors which influenced this outcome differed by race-ethnicity.
Clinical implications: Understanding patient characteristics associated with primary nonadherence may be important for disease management, because many patients with asthma do not fill their ICS prescriptions.