Reliability, validity and responsiveness of a revised scoring system for the Liverpool Seizure Severity Scale

This report examines the reliability, validity and responsiveness of a revised scoring system for the Liverpool Seizure Severity Scale (LSSS). The revised scoring system was validated using archival data from an observational study and a randomized controlled study. Factor analyses confirmed that a single dimension captured how patients evaluate the severity of their most severe seizures occurring during a recall period. The revised scoring system repositions the severity score to range from 0 (no seizures) to 100 (most severe possible). Scores based on the new system were reliable, had construct validity (known-groups validity), and were responsive to changes in the patients' epilepsy as noted by their physicians. Results suggest that future epilepsy studies assessing seizure severity should incorporate the revised LSSS scoring system and a modified version of the questionnaire that simplifies self-assessment and analyses. The modified version of the LSSS and its scoring system are appended to this report.