Using observational analysis of multiple sclerosis relapse to design outcomes-based contracts for disease-modifying drugs: a feasibility assessment

Abstract

Objective:

To assess predictors and costs of multiple sclerosis (MS) relapse, a potential outcome measure in payer-manufacturer risk-sharing agreements for disease-modifying drugs (DMDs).

Methods:

A retrospective cohort analysis of medical/pharmacy claims was used. Study patients had ≥1 DMD (interferon beta, glatiramer, natalizumab) claim, without DMD claims in a 6-month pre-period before DMD initiation; were aged 18–64 years and continuously enrolled from the pre-period through a 24-month post-period; and had ≥2 MS medical claims during the 30-month study period. Post-period relapse cohorts included: (1) severe (hospitalization with MS diagnosis); (2) moderate (outpatient services including intravenous methylprednisolone); and (3) none. Poisson regression modeled severe relapse frequency, logistic regression modeled ≥1 severe relapse, and generalized linear modeling predicted healthcare costs. Tested predictors included demographics, insurance type, index DMD, pre-period health status, and DMD medication possession ratio (MPR).

Results:

Severe relapse was experienced by 14.5% and moderate relapse by 13.8% of 2291 patients. In logistic regression, severe relapse was predicted by plan type; age (odds ratio OR]?=?1.018, 95% confidence interval CI]?=?1.005–1.031); pre-period Charlson Comorbidity Index (OR?=?1.307, 95% CI?=?1.166–1.464); pre-period proxy measure indicating impaired activities of daily living (OR?=?1.470, 95% CI?=?1.134–1.905); pre-period MS hospitalization (OR?=?2.174, 95% CI?=?1.537–3.074); and DMD non-adherence (MPR OR?=?0.101, 95% CI?=?0.068–0.151). Poisson regression results were similar. Predicted mean standard deviation] all-cause healthcare expenditures were tripled for patients with severe compared with moderate relapse ($48,173 $8665] and $13,334 $1929], respectively).

Limitations:

Commercially insured patients from a single payer; use may have been inconsistent with approved indications; proxy relapse measure may have misclassified patients.

Conclusions:

Severe MS relapses requiring hospitalization, although affecting less than 15% of patients initiating DMD treatment, are associated with high medical costs. The only actionable predictor of severe relapse identified in observational analysis was MPR, raising questions about the feasibility of using observational data to guide outcomes-based contracting.