The Personal Impact of Epilepsy Scale (PIES)

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Abstract

The impact of epilepsy is manifest by effects related to seizures and side effects of therapy and comorbidities such as depression. This report describes the development of a brief patient-reported outcome (PRO) instrument, the Personal Impact of Epilepsy Scale (PIES), to measure the influence of epilepsy overall and in each of these domains.Instrument development followed standard procedures and an FDA Guidance. People with epilepsy were surveyed with open-ended questions to derive major themes of their concerns, resulting in 4 key areas: seizures, side effects, comorbidities, and overall quality of life (QOL). A preliminary set of 152 questions was based on these themes and completed by 50 patients, age 42.7 (range: 21-71) years, concurrent with comparator instruments, including the NH Seizure Severity Scale (NHSSS), the Liverpool Adverse Events Profile (LAEP), the Quality of Life in Epilepsy (QOLIE-31) scale, the Beck Depression Inventory, and the Epilepsy Foundation Depression: A Checklist. A multiple regression model indicated which PIES measures were associated with scores from the comparator instruments. Questions in each of the domains were selected for correlations and nonduplication. Test-retest consistency at a 3-day interval was completed by 38 subjects and a final set of questions constructed.The final question set comprised 25 items: 9 about characteristics of seizures, 7 about medication side effects, 8 about comorbidities, and 1 about overall quality of life. All items had 5 response choices (0-4), with higher scores reflecting more negative status. A total of 46 subjects completed the 25 questions. Cronbach's alpha was 0.87, indicating good internal consistency. Each of the three domains correlated well with the overall QOL item. The questions pertaining to seizures correlated with the NHSSS, the side effect questions with the LAEP, and the comorbidity questions with the QOLIE-31.The PIES provides a simple, brief PRO measure as a profile of overall impact of seizures, medication side effects, comorbidities, and overall QOL for people with epilepsy. Further study will explore sensitivity to change quantification of the minimal clinically significant change.

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