Abstracts

Rationale: The goal of antiepileptic drug (AED) treatment is to control seizure events. However, AEDs are associated with an increased risk of central nervous system (CNS) events. This study aimed to estimate the economic burden of CNS events in patients with partial onset seizures (POS) treated with AEDs. Methods: Adult patients (aged 18-65) with 2 POS diagnoses (ICD-9 codes 345.4, 345.5, or 345.7) were identified in Truven Health Analytics MarketScan databases (01/2008-12/2011). Patients were classified into two mutually exclusive cohorts (i) CNS and (ii) CNS-free based on whether or not they had a diagnosis for a CNS event. A combination of exact and propensity score matching algorithm in a 1:1 ratio was used for identifying matched pairs. The index date was defined as 30 days before the first CNS event diagnosis for CNS patients and a randomly selected date for CNS-free patients. In both cohorts, the index date was followed by 30 consecutive days of oral AED use in monotherapy. All-cause and epilepsy/seizure-related healthcare resource utilization (HRU) and costs were assessed during the study period (6-month period following the index date) and compared between CNS and CNS-free patients using generalized linear regression and two-part regression models. Multivariate regression models adjusted for potential confounding factors and random effects accounted for the correlation within matched pairs. Costs were measured from a payer s perspective; adjusted for inflation and reported in March 2013 USD. Results: A total of 6,611 patients met the selection criteria (CNS-free: 72%; CNS: 28%), of which 1,369 matched pairs were selected. After matching, the average age in both cohorts was 42.6 years and 58% of patients were female. Most common first CNS events were worsening of seizures (42%), asthenia/fatigue/tiredness (13%), and headache (10%). Over the 6-month study period, CNS patients had higher incidence rates of inpatient (IP) days (0.799 vs. 0.082; incidence rate ratios [IRRs] = 13.78), IP admissions (0.148 vs. 0.016; IRR=8.86), emergency room visits (0.340 vs. 0.056; IRR=5.94), and outpatient visits (7.706 vs. 3.879; IRR=2.03) compared to CNS-free patients (all p<0.01). CNS patients also incurred more epilepsy/seizure-related medical services than CNS-free patients (all p<0.01). Similarly, CNS patients incurred higher costs compared to CNS-free patients with 6-month average all-cause total, pharmacy, and medical costs of $9,003, $1,887, and $7,116 compared to $2,881, $1,454, and $1,427, respectively. CNS patients had all-cause IP, emergency room, and outpatient cost differences of $3,217, $302, and $2,138, of which 82%, 61%, and 38% of the differences were epilepsy/seizure-related, respectively (all p<0.01). Altogether, CNS patients incurred incremental medical costs of $5,949 and incremental pharmacy costs of $378 (all p<0.01). Conclusions: This analysis suggests that the economic burden of CNS events (most commonly seizure-related) in patients with POS is considerable, with costs >