Abstracts

Rationale: Epilepsy affects 1% of the world’s population, with most new cases occurring in childhood and in old age. Despite introduction of new antiseizure medications (ASMs) in recent years, about one third of patients with epilepsy have seizures refractory to pharmacotherapy. The International League Against Epilepsy (ILAE) proposed in 2010 that drug resistant epilepsy (DRE) be defined as failure of adequate trials of two tolerated, appropriately chosen and used ASM schedules to achieve sustained seizure freedom. A validation of the epilepsy diagnosis in the Danish National Patient Registry (DNPR) was last conducted in 2007. The main purposes of this study were to perform a validation of the epilepsy diagnosis in the DNPR, and to identify DRE and its predictors in the validated epilepsy cohort, based on ILAE criteria.

Methods: We identified all individuals who were registered with a first diagnosis of epilepsy or seizures in the Neurology Department, Aarhus University Hospital, Denmark between 2010 and 2019. We reviewed electronic patient records on a random sample of these patients and validated the epilepsy diagnosis as well as subtype classification according to ILAE criteria. In the validated cohort of patients with confirmed incident epilepsy, we estimated the proportion that fulfilled ILAE’s definition of DRE at the time of the latest hospital contact.

Results: We identified 7,500 patients with a first diagnosis of epilepsy or seizures at the Department of Neurology, Aarhus University Hospital from 2010 to 2019. We reviewed the medical records on a sample of 194 patients. Of these, 168 were registered with an epilepsy diagnosis and 26 with a seizure diagnosis. The epilepsy diagnosis was confirmed in 157 of 168 cases, providing a positive predictive value (PPV) of 94% (95% CI: 88%-96%). Among persons registered with a seizure diagnosis, 5 of 26 had epilepsy (PPV 19%, 95% CI: 8%-39%). Among the 157 confirmed epilepsy cases in the DNPR, 91 were coded as focal epilepsy, 25 as generalized epilepsy and 41 (26%) were coded as unclassifiable epilepsy. The PPV of focal epilepsy in the DNPR was 86% (95% CI: 78%-92%), and the PPV of generalized epilepsy was 80% (95% CI: 60%-91%). Among the 162 validated epilepsy cases, 62 (38%, 95% CI: 32%-47%) were incident cases and 100 (62%, 95% CI: 55%-70%) were prevalent cases.
_x000D_ In the sample of 62 individuals with confirmed incident epilepsy, 32 (52%, 95% CI: 39%-64%) were categorized as responsive to ASM treatment, 20 (32%, 95% CI: 22%-45%) were categorized as undetermined, whereas 10 individuals (16%, 95% CI: 9%-27%) fulfilled the definition of drug resistant epilepsy.

Conclusions: In the Danish National Patient Registry, we found a high PPV of the epilepsy diagnosis. Among persons identified with incident epilepsy, 16% of fulfilled ILAE criteria of drug resistant epilepsy. Further analyses, including identification of predictors of drug resistance, will be conducted on a sample of all individuals registered with epilepsy or seizure codes from 2010 to 2019 in the Region of Central Jutland, Denmark.

Funding: This research projected was funded by the Lundbeck Foundation and the Novo Nordisk Foundation (NNF16OC0019126).