Abstracts

Rationale: Definitions of drug-resistant epilepsy (DRE) based on the number of distinct antiseizure medications (ASMs) in claims databases have been suggested (Hill et al. Neurology 2021:97:e1343-e1350). This study aims were to explore identifying DRE using administrative claims, to describe healthcare resource utilization (HCRU), costs, and specific events overall and according to number of ASMs, and to identify factors associated with increasing number of ASMs.

Methods: Cohort study using administrative MarketScan data (selection period: 01/01/2009 to 03/01/2017) of insured patients with an epilepsy diagnosis (ICD-9: 345.X, 780.39; ICD-10: G40.X, R56.9) within the 12-month pre-index (baseline) period, a second fill of their first prescribed ASM (date of second fill=index date) during the selection period, and 12-month post-index enrollment. Year 1 number of distinct ASMs (1, 2, 3, ≥4), HCRU, and costs were evaluated among a subset of patients with ≥1 year of follow-up. Factors associated with increasing numbers of ASMs were evaluated using Cox proportional hazards regression over up to 3 years (no requirement for post-index enrollment).


Results: At 1 year follow-up, 61,945 patients received 1 ASM (n=50,548), 2 ASMs (n=9552), 3 ASMs (n=1574) and ≥4 ASMs (n=271). At baseline, patient characteristics and mean HCRU were generally similar across subgroups (Table). At 1 year follow-up, patients with more ASMs had a higher mean number of all-cause claims/year for inpatient (1, 2, 3, ≥4 ASMs, respectively: 0.4, 0.7, 1.0, 1.4), outpatient (1, 2, 3, ≥4 ASMs: 96.1, 124.8, 150.6, 162.6), and pharmacy (1, 2, 3, ≥4 ASMs: 45.2, 55.4, 65.6, 69.9) services. Similar trends were observed for epilepsy-related claims in inpatient (1, 2, 3, 4 ASMs: 0.1, 0.4, 0.7, 1.1), outpatient (1, 2, 3, ≥4 ASMs: 7.5, 16.8, 28.9, 42.1), and pharmacy (1, 2, 3, ≥4 ASMs: 8.5, 14.0, 19.4, 26.0) services. Associated costs/year also increased (Figure). Rates (per 1000 person-years) for events of interest increased with increasing number of ASMs; the highest rates (reported for 1, 2, 3, ≥4 ASMs) were for other nervous system disorders (522.3, 775.6, 1016.2, 1284.5), other aftercare (443.9, 631.1, 769.8, 826.1), mood disorders (324.5, 511.7, 681.3, 756.5), anxiety disorders (246.3, 382.7, 526.7, 579.3), and migraine (197.9, 360.8, 513.8, 633.0). Factors associated with two ASMs were brain tumor (hazard ratio [95% confidence interval]: 1.40 [1.29‒1.52]), abnormal electroencephalogram (1.24 [1.15‒1.34]), status epilepticus (1.22 [1.13‒1.31]), depression (1.14 [1.10‒1.18]), headache (1.12 [1.09‒1.16]), anxiety (1.09 [1.05‒1.13]), and head injury (1.05 [1.01‒1.09]). Factors associated with three ASMs were similar to two ASMs (except for head injury); factors for four ASMs were anxiety, brain tumor, depression, and headache.

Conclusions: The study population had similar HCRU at baseline, but patients with more ASMs during follow-up had a higher number of claims, costs, and events of interest rates. Factors associated with increasing number of ASMs expand on those reported in the literature (Xue-Ping et al. Medicine 2019;98:30(e16402)).

Funding: UCB Pharma-sponsored.