Estimating the prevalence of treated epilepsy using administrative health data and its validity: ESSENCE study

Background and Purpose Few of the epidemiologic studies of epilepsy have utilized well-validated nationwide databases. We estimated the nationwide prevalence of treated epilepsy based on a comprehensive medical payment database along with diagnostic validation. Methods We collected data on patients prescribed of antiepileptic drugs (AEDs) from the Health Insurance Review and Assessment service, which covers the entire population of Ko­rea. To assess the diagnostic validity, a medical records survey was conducted involving 6,774 patients prescribed AEDs from 43 institutions based on regional clusters and referral levels across the country. The prevalence of treated epilepsy was estimated by projecting the diag­nostic validity on the number of patients prescribed AEDs. Results The mean positive predictive value (PPV) for epilepsy was 0.810 for those prescribed AEDs with diagnostic codes that indicate epilepsy or seizure (Diagnosis-E), while it was 0.066 for those without Diagnosis-E. The PPV tended to decrease with age in both groups, with lower values seen in females. The prevalence was 3.84 per 1,000, and it was higher among males, chil­dren, and the elderly. Conclusions The prevalence of epilepsy in Korea was comparable to that in other East Asian countries. The diagnostic validity of administrative health data varies depending on the method of case ascertainment, age, and sex. The prescriptions of AEDs even without relevant diagnostic codes should be considered as a tracer for epilepsy.