Good Degree of Agreement in Categorizing Epilepsy Treatment Response According to ILAE Criteria

Doctor reading medical chart
Doctor reading medical chart
Investigators assessed interrater agreement in categorizing treatment outcomes and drug responsiveness status according to the International League Against Epilepsy definition of drug-resistant epilepsy.

Interrater agreement in categorizing drug responsiveness status and treatment outcomes according to the International League Against Epilepsy (ILAE) definition of drug‐resistant epilepsy is moderate to almost perfect, according to new study results published in Epilepsia.

Researchers consecutively enrolled 1053 patients with focal epilepsy (mean age, 44.5±14.2) who met ILAE criteria for drug resistance. Patients had been treated at 43 centers and were followed-up prospectively for 18 to 34 months. Individual investigators and 2 rotating members of a 16‐member expert panel retrospectively reviewed and categorized treatment outcomes for all antiepileptic drugs (AEDs) used up to time of enrollment as well as outcomes of newly introduced AEDs at enrollment. Cohen’s kappa (k) statistics were used to test interrater agreement.

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There was an almost-perfect agreement between panel members in categorizing outcomes on newly introduced AEDs at time of enrollment (90.1%; k=0.84; 95% CI, 0.80‐0.87). Moderate agreement was found between the expert panel and individual investigators (70.4%; k=0.57; 95% CI, 0.53‐0.61). Agreement was 91.7% between expert panel members in the categorization of outcomes on previously used AEDs (k=0.83; 95% CI 0.81‐0.84), whereas agreement was 68.2% between the panel members and investigators (k=0.50; 95% CI, 0.48‐0.52). Disagreement was mostly related to treatment failures or undetermined outcomes as categorized by the investigators and expert panel members, respectively. Approximately 19% of patients with drug‐resistant epilepsy as determined by the investigators were categorized as having “undefined responsiveness” by the experts.

Limitations of the study included the retrospective analysis of outcomes and the inclusion of only patients with drug-resistant focal epilepsy.

Approximately “1 of 5 patients enrolled by investigators with a diagnosis of drug resistance were not deemed to meet criteria for drug resistance by the expert panel,” the researchers wrote. “Despite the subjective limitations of categorizing treatment outcomes, these data suggest that drug resistance may be over-diagnosed in clinical practice.”


Zaccara G, Mula M, Ferrò B, et al. Do neurologists agree in diagnosing drug resistance in adults with focal epilepsy? Epilepsia. 2019;60(1):175-183.