Development of a patient-reported outcome measure for psychotherapeutic interventions in people with seizures: A mixed methods study.

BACKGROUND: Generic or even disease-specific quality of life measures are unlikely to be equally responsive to different epilepsy treatment modalities, such as pharmacotherapy, surgery, or psychotherapy. The purpose of the present study was to summarize the development of a patient-reported outcome measure (PROM) designed to be particularly sensitive to change mediated by psychotherapeutic interventions in people with seizures. METHODS: The development of this instrument involved seven steps: (1) Development of a candidate item set based on the outcome of previous qualitative research, (2) initial quantitative-descriptive study yielding an assessment of content validity by clinical experts, (3) qualitative-descriptive posttherapy cognitive debriefing interviews with patients with epileptic and/or nonepileptic seizures (NES), (4) English translation, (5) elicitation of qualitative feedback from international experts, (6) assessment of internal consistency and correlation with similar previously validated generic and epilepsy-specific measures in a pilot study, and (7) final expert content validity rating. RESULTS: (1) The candidate item set comprised 29 stem items; five of which were followed by a follow-up (FU) item that refers to the statement of the stem item. (2) Eight clinical experts assessed content validity. Informed by rating and experts' qualitative comments, 15 items remained unchanged, eleven underwent substantial revisions, three were excluded, and six added. (3) Cognitive debriefing interviews were conducted with 14 patients with epilepsy and/or NES. Based on the interviewees' feedback, 29 of 32 items remained unchanged, two were excluded, one reworded, and four added. (4) The forwards-backwards English translation prompted substantial revision of two items because the verbatim back translation of the corresponding English items was conceptually more convincing than the original German wording. (5) The international experts identified problems with item comprehensibility/clarity of four stem and three FU items that were subsequently reworded. Ten items were added to incorporate their qualitative feedback resulting in a total of 44 items. (6) Thirty-one patients with epilepsy participated in the pilot study. The overall internal consistency of the self-Efficacy, Assertiveness, Social support, self-awareness, and hElpful thinking in people with seizures (EASE) was very good (α = 0.92). Analysis at item-level revealed problems with inverted and self-evident items. Based on this analysis, three items were eliminated and two items were revised (one FU item was turned into a stem item) resulting in a total of 42 items. (7) The second content validity rating showed final item-content validity indices (I-CVIs) between 0.38 and 1 and an excellent mean CVI of 0.92 at scale level (S-CVI/ave). Fourteen stem items were substantially revised by incorporating the experts' qualitative feedback, three items with low I-CVIs were excluded, and one item was added. The final questionnaire consisted of 40 stem items; eight of which include at least one FU item. CONCLUSION: Based on these results, the EASE is valid in terms of content, internally consistent, clear, and acceptable to patients with seizures. The measure has now been developed to the stage at which the validity and reliability as well as the psychometric properties and factorial structure of the new instrument can be assessed in larger patient groups in a prospective clinical study.