Interrater reliability of Engel, International League Against Epilepsy, and McHugh seizure outcome classifications following vagus nerve stimulator implantation

Abstract

Object Interrater reliability as measured by the kappa (κ) statistic is a widely used and valuable tool to measure the robustness of a scoring system. Seizure frequency reduction is a central outcome measure following vagus nerve stimulation (VNS). A specific VNS scoring system has been proposed by McHugh, but its interrater reliability has not been tested. The authors assessed its interrater reliability and compared it with that of the Engel and International League Against Epilepsy (ILAE) systems. Methods Using the Engel, ILAE, and McHugh scoring systems, 3 observers independently rated the medical records of children who had undergone vagus nerve stimulator implantation between January 2001 and April 2011 at the Southampton University Hospital. The interrater agreements were then calculated using the κ statistic. Results Interrater reliability for the McHugh scale (κ0.693) was very good and was superior to those of the Engel (κ0.464) and ILAE (κ0.491) systems for assessing outcome in patients undergoing VNS. Conclusions The authors recommend considering the McHugh scoring system when assessing outcomes following VNS.