A validation of the new definition of drug‐resistant epilepsy by the International League Against Epilepsy

Abstract

SUMMARYObjective: To establish applicability, the recently proposed International League Against Epilepsy (ILAE) consensus on drug-resistant epilepsy (DRE) requires testing in clinical and research settings. This study evaluates the reliability and validity of these criteria in a clinical population. Methods: In phase I, two independent evaluators reviewed 97 randomly selected medical records of patients with epilepsy at two separate intervals. Both ILEA consensus and standard diagnostic criteria were employed. Kappa, weighted kappa, and intraclass correlation coefficient (ICC) were used to determine interobserver and intraobserver variability. In phase II, ILAE consensus criteria were applied to 250 patients with epilepsy to determine risk factors associated with development of DRE and to calculate point prevalence.Results: The interobserver agreement of the four definitions was as follows: Berg (0.56), Kwan and Brodie (0.58), Camfield and Camfield (0.69), and ILAE (0.77). The intraobserver agreement of the four definition was as follows: Berg (0.81), Kwan and Brodie (0.82), Camfield and Camfield (0.72), and ILAE (0.82). The prevalence of DRE was the following: with the Berg's definition was 28.4%, Kwan and Brodie 34%, Camfield and Camfield 37%, and with ILAE was 33%. Significance: This is first study to establish reliability and validity of ILAE criteria for the diagnosis of DRE. This new definition compares favorably with previously established constructs, which continue to retain clinical significance. KEY WORDS: Drug-resistant epilepsy, Validation, Reliability, Validity, Consensus.Epilepsy affects 50 million people worldwide.1 It is estimated that between 6% and 69% of patients fail to respond to standard medical and surgical therapies and continue to experience debilitating refractory seizures. These patients are classified as having drug-resistant epilepsy (DRE), a diagnosis with poor prognostic implications that include premature death, physical injury, psychosocial dysfunction, and reduced quality of life.2,3 The prevalence of DRE is not consistently defined and tends to vary among studies, owing to issues with population selection, sample size, classification, terminology, and characterization of seizure intractability. 1,4,5 Conceptual elements of DRE are documented in the literature with terminology that is nonstandard and potentially conflicting, albeit abundant. Various prefixes such as "pharmaco-resistant-," "refractory-," "drug refractory-," or "intractable-" have been applied to describe this form of epilepsy. Recognizing the need for a consistent definition to guide classification, diagnosis, epidemiology, and research, the International League Against Epilepsy (ILAE) generated the unified concept of DRE in 2008. Two years prior, Berg et al. 6 applied six different definitions of DRE to a cohort of 613 children with newly diagnosed epilepsy. Of these six criteria, three diagnostic criteria-namely those proposed by Camfield and Camfield,7 Kwan and Brodie, 8 and Berg's own 9,10 -produced the high...

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