Abstracts

Rationale: VNS implant is an adjunctive therapy to antiepileptic drugs (AEDs) in patients 12 years or older with refractory partial-onset seizures that are not controlled with medication alone. The purpose of this study is to evaluate the clinical and economic benefits associated with VNS therapy in patients with refractory epilepsy in a real-world setting. Methods: A retrospective cohort study design will be applied, using data from 5 Medicaid State claims databases (01/97-06/09), including Florida, Iowa, Kansas, Missouri, and New Jersey. Patients receiving VNS, who had ?1 neurologist visit with a diagnosis of epilepsy (ICD-9 345.xx, 780.3, or 780.39), ?1 medical procedure claims for VNS implantation, ?1 AED dispensing, and ?6 months of pre- and post-VNS health plan continuous enrollment are included. The pre-index period spanned from the latest of the start of enrollment, first diagnosis for epilepsy, or a prescription filled for an AED until the first VNS implantation date (index date), while the post-index period spans from the index date until the earliest of the VNS removal, death, end of enrollment, or data end date. Patients' observation period was divided into 90-day intervals (i.e. quarter) and outcomes were repeatedly measured at each quarter. Morbidity were measured by frequency of hospitalizations, hospital length of stay, emergency room visits, outpatient visits, neurologist visits, fractures, motor vehicle accident-related injuries, head injuries, and status epilepticus events. Univariate and multivariate Poisson regression models will be used to estimate the incidence rate ratios of the morbidity and mortality outcomes between the pre- and post- index period. Univariate and multivariate regression models were also used to estimate the healthcare cost difference (quarterly) between the pre- and post- index period. Proportion of days covered (PDC) will be used to compare AED adherence (PDC ?0.8 = adherent) between the pre- and post- index period. AED treatment persistence (discontinuation rates and treatment duration) will be reported for the post-index period. Results: Of the 1,846 patients meeting the inclusion criteria, the mean age is 27.6 years and 51.2% are males. On average patients have about 29.5 and 28.4 months of eligibility in the pre- and post-index period, respectively. On average ( SD) patients use 3.2 ( 1.4) different AEDs during the pre-index period, and overall, 81.3% of the patients have ?1 episode of AED polytherapy. Mean Charlson Comorbidity Index ( SD) was 0.61 ( 1.05). Proportions of patients with psychiatric comorbidities were 27.8% (depression), 14.8% (anxiety disorders), and 8.7% (bipolar disorder). 86.3% patients used antimicrobial agents and 56.7% patients used antipsychotic drugs. The analyses for clinical and economic outcomes are in progress; results will be available for the conference presentation. Conclusions: Based on a sample of over 1,800 VNS patients, the clinical and economic outcomes before vs. after VNS therapy will be presented.