Cost-sharing and initiation of disease-modifying therapy for multiple sclerosis

To assess the effects of patient cost sharing on initiation of disease-modifying therapies (DMTs) in multiple sclerosis (MS).

Retrospective claims database study of privately insured patients newly diagnosed with MS between 2004 and 2008 from 33 large employers.

We assessed the effects of plan-level cost-sharing on DMT initiation during a 2-year follow-up period after diagnosis. Incident cases were identified by 2 or more claims with ICD-9 codes for MS within a year, subsequent to a year with no such claims. Covariates for adjustment included age, gender, relationship to primary beneficiary, comorbid conditions, and calendar year, as well as unobserved factors that did not vary within plans over time.

Out of a sample of 3460 patients meeting criteria for inclusion, only 17% initiated a DMT within 2 years of diagnosis. An increase in the cost-sharing rate from zero to the 95th percentile (17.8%) was predicted to decrease initiation within 2 years of diagnosis by 2.9 percentage points, or 12.7% (P = .019).

High cost-sharing is associated with delayed initiation of effective MS therapies.