Very good inter-rater reliability of Engel and ILAE epilepsy surgery outcome classifications in a series of 76 patients

The inter-rater reliability, expressed as kappa score, k, of the Engel and International League Against Epilepsy (ILAE) classifications of epilepsy surgery seizure outcome has not previously been evaluated. In a consecutive series of 76 patients (40 male; 25 children), 75 undergoing resective and 1 disconnective surgery at a mean age of 27.5 years (13 months–62 years), one observer classified 88% (n = 67) and a second observer classified 87% (n = 66) of patients as either Engel I or II (free from or rare disabling seizures) after a median follow up of 36 months (range 12–92 months); comparably, both observers classified 84% (n = 64) as ILAE 1–3. Correlation for Engel versus ILAE for observer 1 was 0.933 (p < .0005) and for observer 2 was 0.931 (p < .0005). Both ILAE (k 0.81, 95% confidence intervals 0.69, 0.91) and Engel (k 0.77, 95% CI 0.65, 0.87) classifications have very acceptable inter-rater reliability as well as significant correlation.