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. 2025 Dec 2:175:110840.
doi: 10.1016/j.yebeh.2025.110840. Online ahead of print.

Psychometric validation of the quality of life Inventory - Disability (QI-Disability) among patients with Lennox-Gastaut syndrome and Dravet syndrome

Drishti Shah  1 , Peter Jacoby  2 , Helen Doll  3 , Hoan Do  4 , J Scott Andrews  5 , Heather Romero  6 , Gregor Gibson  7 , Jenny Downs  8
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Free article

Psychometric validation of the quality of life Inventory - Disability (QI-Disability) among patients with Lennox-Gastaut syndrome and Dravet syndrome

Drishti Shah et al. Epilepsy Behav. .
Free article

Abstract

Backgound: To evaluate the psychometric properties of the Quality of Life Inventory -Disability (QI-Disability) for individuals with Dravet syndrome (DS) or Lennox-Gastaut syndrome (LGS), two rare developmental and epileptic encephalopathy conditions.

Methods: Cross-sectional data for individuals were drawn from the Adelphi DS & LGS Disease Specific Programme including the caregiver-reported QI-Disability and EQ-5D-5L, and physician-reported (7-point Likert scale) rating or quality of life. Factor structure of the QI-Disability was assessed using confirmatory factor analysis with goodness-of-fit statistics and internal consistency was assessed using Cronbach's alpha. Convergent validity was assessed by evaluating relationships between QI-Disability, EQ-5D-5L scores, and physician QOL ratings.

Results: There were 154 patients with DS and 196 patients with LGS. The mean (SD) total QI-Disability score was 57.3 (SD 11.9) for DS and 58.9 (SD 13.8) for LGS. Fit statistics for the 6-factor QI-Disability model were mostly satisfactory; the factor loading for one item was unsatisfactory. Good internal consistency (alpha > 0.7) was found for all QI-Disability domains and for the total score in both LGS and DS groups. Convergent validity was demonstrated with correlations being as expected between QI-Disability and EQ-5D-5L scores, for example, strong correlations between the QI-Disability Physical Health and EQ-5D pain/discomfort dimension scores. There was a mean increase of approximately 3 points in the QI-Disability total score per unit category change in the physician-rated QOL scale.

Conclusions: QI-Disability had mostly satisfactory evidence of validity and reliability for DS and LGS and appears suitable for use in clinical practice and clinical trials.

Keywords: Developmental and epileptic encephalopathy; Dravet syndrome; EQ-5D-5L; Lennox-Gastaut syndrome; Psychometric validation; QI- Disability; Quality of life.

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Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Drishti Shah, Heather Romero are employees of Takeda Development Center Americas, Inc., and own stock or stock options in Takeda Pharmaceutical Company Limited. Peter Jacoby has no potential conflicts of interest to report. J. Scott Andrews was an employee of Takeda Development Center Americas, Inc., at the time of the study and owned stock or stock options in Takeda Pharmaceutical Company Limited. Helen Doll and Hoan Do are employees of Clinical Outcomes Solutions Ltd. Gregor Gibson is an employee of Adelphi Real World. Jenny Downs has consulted for Marinus, Ultragenyx, Acadia, Avexis, Orion, Taysha, Neurogene, Neurocrine and Takeda; and was an associate investigator on clinical trials with Anavex and Newron. All other consultancies are unrelated to this work and all remuneration has been made to her department.

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