Glatiramer acetate and interferon beta-1b: a study of outcomes among patients with multiple sclerosis

To study the medical cost and probability of relapse in patients with multiple sclerosis (MS) treated with either glatiramer acetate (GA) or interferon beta-1b (IFN beta.1b).

Data were obtained from the i3 InVision Data Mart Database from July 2001 to June 2006. We established an "intent-totreat" (ITT) cohort (n=842) of patients diagnosed with MS who began treatment with either GA or IFN beta-1b and had continuous insurance coverage from 6 months before to 2 years after the date when they began taking the medication. We also created a "continuous use" (CU) cohort (n=418) of individuals who, in addition to the criteria listed above, used either GA or IFN beta-1b within 28 days of the end of the 2-year postperiod. Using multivariate regressions, we examined both the 2-year total average direct medical costs and the likelihood of relapse within this period associated with the use of each of these MS medications. We defined relapse as being either hospitalization with a principal diagnosis of MS or having an outpatient visit with a diagnosis of MS and then prescribed steroids within a 7-day period. All regression analyses controlled for a wide range of factors that may potentially affect outcomes.

In the ITT cohort, patients who started treatment with GA had a significantly lower 2-year estimated risk of relapse (13.54% vs. 5.31%; P=0.0006). In the CU cohort, patients who used GA also had a significantly lower 2-year estimated risk of relapse (10.91% vs. 2.09%; P=0.0018), as well as significantly lower average total medical costs ($53,157 vs. $48,130; P=0.0345).

Results from this study indicate that users of GA have a significantly lower probability of 2-year relapse than users of IFN beta-1b. In addition, among continuous users, the 2-year total average direct medical costs are significantly lower for users of GA than for users of IFN beta-1b.