Development of a new seizure severity questionnaire: initial reliability and validity testing

This report describes the initial steps for development of a new scale to assess seizure severity as a treatment response.

Standard methodology was used to develop the test instrument. Item generation was performed by selecting items from other questionnaires, and asking patients and epileptologists about seizure components. Face and content validity were assessed in a pilot study with patients and observers. The questionnaire was formatted as a structured interview for a reliability study. Construct validity was assessed with three existing questionnaires. Inter-rater reliability and test-retest reliability were performed as two independent ratings on one day, and one re-interview.

Based on item generation and pilot testing (33 patients, 28 observers), the Seizure Severity Questionnaire (SSQ) was organized into warning, activity-movement, and recovery (cognitive, emotional, and physical aspects) stages of seizures. Questions reviewed duration, severity, bothersomeness and overall ratings, and the most bothersome aspect of seizures. The mean SSQ Summary Score was 5.78+/-3.24, inter-rater reliability was 0.76 (N=91), and test-retest reliability was 0.74 (N=63). Construct validity showed statistically significant correlations with other scales.

This study has explored the psychometric properties of the SSQ for face and content validity, inter-rater and test-retest reliability, and construct validity. The Summary Score reliably represents the major components of seizures.