Validation of the Seizure-Related Impact Assessment Scale: A Novel Patient-Reported Outcome Measure for Epilepsy

There is a clear need in epilepsy clinical trials and practice for a measure that captures the trade-off between seizure and treatment-related adverse effects, which is reliable over time and across different treatment regimens. We aimed to create and validate the Seizure-Related Impact Assessment Scale (SERIAS) to fill this need.

This was a prospective longitudinal study of adults with epilepsy recruited from an Australian comprehensive epilepsy center. Participants completed SERIAS at baseline and 3 and 6 months later. SERIAS has 6 self-report items. Five items record the number of days per month that seizures or treatment-related adverse effects partially or fully affect work/home/school and family/social/nonwork activities. The final item is an epilepsy disability visual analog scale. SERIAS is scored by adding the days per month of disability, with scores ranging from 0 to 150 (higher scores indicate more disability). SERIAS was completed alongside 7 validated instruments measuring seizure-related and treatment-related adverse effects (Work and Social Adjustment Scale [WSAS], Liverpool Adverse Events Profile [LAEP]), mood disorders (Neurological Disorders Depression Inventory for Epilepsy [NDDI-E], Generalized Anxiety Disorder [GAD-7]), somatic symptoms (Somatic Symptom Scale [SSS-8]), and quality of life (Quality of Life in Epilepsy Inventory [QOLIE]-31, EuroQol 5 Dimensions [EQ-5D]). General linear mixed models were used to investigate the relationship between the SERIAS and other relevant clinical and psychometric data. Standardized model coefficients β are presented with 95% confidence intervals.

A total of 90 patients (64.4% female, mean age 43.1 years) completed baseline SERIAS. Most patients reported at least 1 day of disability (62%, median SERIAS score = 3, interquartile range = 18.3). Greater disability was negatively correlated with QOLIE-31 total score (β = -0.17, 95% CI -0.27 to -0.07) and positively correlated with scores on 5-level EQ-5D (β = 0.15, 95% CI 0.04-0.25), NDDI-E (β = 0.22, 95% CI 0.13-0.31), GAD-7 (β = 0.21, 95% CI 0.09-0.32), SSS8 (β = 0.29, 95% CI 0.17-0.41), LAEP (β = 0.29, 95% CI 0.20-0.39), WSAS seizure-related adverse events (β = 0.23, 95% CI 0.14-0.33), and WSAS treatment-related adverse events (β = 0.36, 95% CI 0.26-0.46). Higher seizure frequency was associated with higher SERIAS score (β = 0.07, 95% CI 0.03-0.11). Psychometric reliability for the SERIAS was acceptable (all coefficients >0.70) as was test-retest reliability (n = 35 patients, intraclass correlation coefficient = 0.72, 95% CI 0.51-0.85).

SERIAS shows good psychometric reliability and strong test-retest stability. These findings suggest that SERIAS is a valid scale to measure epilepsy-related disability.