Abstract
Purpose:
To compare adherence and persistence among patients with multiple sclerosis (MS) initiated on disease-modifying therapy (DMTs), including intramuscular (IM) interferon beta-1a (IFNβ-1a), subcutaneous (SC) IFNβ-1a, IFNβ-1b, or glatiramer acetate (GA).
Methods:
MS patients initiated on IM-IFNβ-1a, SC-IFNβ-1a, IFNβ-1b, or GA between January 1, 2000 and January 2, 2008 were identified from a retrospective claims database study associated with a large US health plan. The date of DMT initiation was the index date; patients were observed for 6 months before and 12–36 months after the index date. Adherence to the index DMT was measured with a medication possession ratio (MPR), the proportion of days patients possessed their index DMTs; MPR ≥ 0.80 was considered adherent. Persistence was time in days from index date until the earlier of a minimum 60-day gap in DMT therapy or the last DMT claim during follow-up. Adherence and persistence were modeled with logistic and Cox proportional hazard regressions, respectively.
Results:
The study population comprised 6,680 patients in the DMT cohorts: IM-IFNβ-1a (N = 2,305, 34.5%); IFNβ-1b (N = 894, 13.4%); GA (N = 2,270, 34.0%); and SC-IFNβ-1a (N = 1,211, 18.1%). The IM-IFNβ-1a cohort had significantly higher regression-adjusted odds of adherence relative to the other cohorts: 52.4% higher odds versus the IFNβ-1b cohort (OR = 0.656, CI = 0.561–0.768); 33.5% higher odds versus the GA cohort (OR = 0.749, CI = 0.665–0.844); and 20.6% higher odds versus the SC-IFNβ-1a cohort (OR = 0.829, CI = 0.719–0.957). There were no consistent differences in persistence between the cohorts.
Conclusion:
IM-IFNβ-1a patients had significantly higher odds of adherence compared with other DMT cohorts, possibly attributable to IM-IFNβ-1a’s less frequent dosing schedule. The benefits of adherence may include better quality of life, lower risk of relapse, and fewer hospitalizations and emergency visits, making adherence a critical component of MS management.
Acknowledgments/disclosure
Support for this study was provided by Biogen Idec. Dr. Agarwal and Ms. Dembek are employees of Biogen Idec. Dr. Halpern and Ms. Borton are employees of i3 Innovus, which was contracted by Biogen Idec to conduct the study. Dr. Lopez-Bresnahan is an employee of i3 Research. Kathy Oneacre provided assistance with medical writing of the manuscript and is an employee of i3 Innovus. Amy O’Donnell, MD, and Tomislav Babic, MD of i3 Research reviewed this manuscript and provided clinical input. Preliminary findings from this study were presented at the American Academy of Neurology 62nd Annual Meeting, April 2010, Toronto, Canada and the 2010 Annual Meeting of the Consortium of Multiple Sclerosis Centers, June 2010, San Antonio, TX, USA.