Impact of medication adherence to disease-modifying drugs on severe relapse, and direct and indirect costs among employees with multiple sclerosis in the US

Abstract

Objective:

To compare rates of severe relapse and total direct and indirect costs over a 2-year period between US-based employees with multiple sclerosis (MS) who were adherent and non-adherent to disease-modifying drugs (DMDs).

Methods:

Employees with ≥1 MS diagnosis (ICD-9-CM: 340.x) and ≥1 DMD pharmacy claim between 1/1/2002–12/31/2007 were identified from a large US administrative claims database. Patients had continuous coverage ≥6 months before (baseline) and ≥24 months after (study period) their index date (first DMD claim). Adherence was measured using medication possession ratio (MPR) over the study period. Patients with MPR ≥80% were considered adherent (n = 448) and those with MPR <80% as non-adherent (n = 200). Multivariate analyses were used to compare rates of severe relapse (inpatient or Emergency Department visit with MS diagnosis) and costs in 2007 dollars between DMD adherent and non-adherent patients. Direct costs were calculated as reimbursements to providers for medical services and prescription drugs excluding DMDs. Indirect costs included disability and medically-related absenteeism costs.

Results:

DMD adherent patients were on average older (43.5 vs 41.8 years, p = 0.015) and more likely to be male (38.6% vs 26.0%, p = 0.002) compared with non-adherent patients. Adherent patients had lower rates of depression, higher rates of previous DMD use, and higher baseline MS-related costs. After adjusting for differences in baseline characteristics, DMD adherent patients had a lower rate of severe relapse (12.4% vs 19.9%, p = 0.013) and lower total (direct and indirect) costs ($14,095 vs $16,638, p = 0.048) over the 2-year study period.

Conclusions:

In this study, DMD adherence was associated with a significantly lower rate of severe relapse and lower total costs over 2 years. Causality cannot be inferred because adherence and outcomes were measured over the same period. The study was subject to limitations associated with use of claims data and the absence of clinical measures.

Key words::

• Disease-modifying drugs
• Multiple sclerosis
• Adherence
• Costs
• Relapse

Abbreviations::

• DMD, disease-modifying drug
• MS, multiple sclerosis

Transparency

Declaration of funding

Research funding for this study was provided by EMD Serono, Inc., Rockland, MA and Pfizer, Inc., New York, NY to Analysis Group, Inc.

Declaration of financial/other relationships

JI, RB, and HB are employees of Analysis Group, Inc. AP and DM are employees of EMD Serono, Inc., Rockland, MA. MS is an employee of Pfizer, Inc., New London, CT. AP, DM, and MS provided feedback on the development of the analysis plan, reviewed study results and manuscript; provided feedback on manuscript, and approved the final manuscript.

Acknowledgments

The peer reviewers on this manuscript have disclosed any relevant financial relationships.