Comparison of the adherence and persistence to inhaled corticosteroids among adult patients with public and private drug insurance plans.

BACKGROUND: Despite important differences in reimbursement procedures between private and public drug insurance plans in Quebec (Canada), no study has evaluated the impact of the type of drug insurance on the use of essential medications such as inhaled corticosteroids (ICS). The lack of data might be attributable, at least in part, to the absence of a provincial medication database for patients with private drug insurance.

OBJECTIVES: To compare patient's adherence and persistence to ICS between Quebec residents (Canada) with private and public drug insurance.

METHODS: A matched cohort design with patients selected from the database of the Régie de l'assurance maladie du Québec (RAMQ) and from reMed, a database that we have put in place for Quebec residents covered by a private drug insurance, was used. ICS users with private drug insurance were selected from reMed between 2008 and 2010 and matched to ICS users with public drug insurance selected from the RAMQ database. Patient's adherence, measured with the proportion of prescribed days covered (PPDC) and persistence over one year, was compared between patients privately and publicly insured using linear regression and Cox regression models.

RESULTS: This study included 330 and 1,109 ICS users with private and public drug insurance, respectively. Patients privately insured were significantly less adherent than patients publicly insured (adjusted mean difference of PPDC: -9.7%; 95% CI: -13.2% to -6.5%). Moreover, patients privately insured were found to be 52% more likely to stop ICS during the first year than patients publicly insured (adjusted HR=1.5; 95% CI: 1.2 to 2.0).

CONCLUSIONS: Although adherence and persistence were rather low in both groups, patients with public drug insurance appeared to have greater adherence and persistence to ICS than patients with private drug insurance. Differences in reimbursement policies might explain the observed differences.