Abstracts

Rationale: Reliable, population-based estimation of incidence and prevalence of epilepsy in a large population remains a major challenge making most studies restricted to smaller geographic locus or not representative to the referent population. This study provides methodological techniques to provide reliable estimates of incidence and prevalence in a large population by utilizing validation procedures and multiple data sources in South Carolina.Methods: Persons with epilepsy and seizure disorders were identified from four data sources: Hospital Discharge, Emergency Department, Physician Office, and Behavioral Risk Factor Surveillance System (BRFSS). Persons were identified with broader case ascertainment ICD-9-CM diagnosis codes of 345.x (epilepsy and status epilepticus), 780.31 (febrile seizures), 780.39 (seizure unspecified), 780.2 (syncope), and 293.0 (delirium). Detailed clinical information was abstracted from representative sample of 3,983 persons (5.4%) with these conditions. Sensitivity and predictive value positive (PVP) measures were conducted for each data source by diagnosis codes. Case identification through BRFSS relied on self-report using random -digit dialing telephone survey of 21,480 individuals. Model-based approach was also used to determine prevalence of epilepsy using routinely available surveillance variables in a log-linear model.Results: BRFSS-based prevalence estimate in SC indicate a rate of 2.0% (95% CI: 1.8-2.3) for ever having epilepsy and 1.1% (95% CI: 0.9 -1.2) for active epilepsy. The prevalence rate of active epilepsy derived from healthcare encounters ranges from 0.8% to 0.9% per annum—a statistically comparable rate within the confidence limit of the BRFSS estimate of active epilepsy. Model -based prevalence rate provided a conservative estimate of 0.8% using information from the case-level data on 70,000 individuals in a loglinear model. The estimated annual in Incidence rate of epilepsy for the general population of SC is 3 per 10,000 (0.03%) indicating 1,200 new onset of epilepsy every year. Among all patients with seizure, ICD-9-CM code of 345.x yielded 31% and 96% while 780.39 yielded 93% and 20% for sensitivity and PVP respectively.Conclusions: Robust and reliable estimation of incidence and prevalence of epilepsy in a large population can be achieved when multi-focal data sources are utilized and validation techniques are incorporated.