Abstracts

Rationale: Epilepsy creates a substantial burden for patients and society, characterized by not only high medical and non-medical costs, but also high indirect costs for patients and caregivers due to lost productivity. Improved disease management, through antiepileptic drug (AED) therapy, potentially reduces the burden. A central aim of AED therapy is to control seizures; however, patients may also experience AED-related adverse effects (AEs). AEs can not only increase costs, but also decrease patient quality-adjusted life years (QALYs). This study’s objective was to summarize methods used to estimate costs and benefits, to include AEs and QALYs, from published economic evaluations for AED therapy of chronic epilepsy. Methods: This systematic review included published economic studies using societal perspective or QALY outcomes for AED therapy for chronic epilepsy. An AE impact inventory was created from a drug information resource that identified box warnings and AEs occurring in =10% of patients receiving AEDs. Each article was summarized to include a comparison of AEs considered in economic evaluations using our comprehensive AE impact inventory tool. Results: Of 16 articles identified for inclusion, 15 incorporated QALYs as an outcome, 6 included a societal perspective. All studies included direct medical care costs, few differentiated between who was impacted (payers vs. patients). Nine studies included consideration of breakthrough seizures, however associated cost burden was inconsistent or missing. Inclusion of seizure-related injuries was infrequent and the scope of injury was either missing or lacking clinically relevant detail. Three of 6 societal studies included lost productivity. Of 15 studies using QALYs, 7 used time-trade off to estimate quality-adjustment. The most common generic instrument for quality-adjustment was the EQ-5D and the QOLIE-31, the most common disease-specific. Four of the healthcare payer perspective studies incorporated specific AEs. No studies explicitly included psychiatric AEs (i.e., depression). Of the 6 studies including AEDs associated with kidney stones, only one included AE costs. Conclusions: Future studies should incorporate a societal perspective, which considers all medical and non-medical costs, to better inform both payers and patients. Study design can be improved by recognizing the scope of AED impacts and justifying decisions about inclusion/exclusion of potential risks and benefits. In particular, studies should consider the AE impacts on costs and QALYs. To avoid double counting, AE costs may not be included in a study if quality-adjustments already account for AE impacts. AEs and related costs and impact on QALYs have not been uniformly addressed in previous economic evaluations. For studies using QALY outcomes, statements regarding representativeness of the population used to assess quality-adjustments, and the validity and responsiveness of the instrument used, and the instrument’s ability to assess therapy impacts on AEs and productivity are needed. Funding: Not applicable