Preliminary psychometric validation of a novel patient-based measure evaluating outcomes following treatment for functional seizures

Abstract

Background

A consistent measure of patient reported outcomes following treatment for functional seizures is lacking. This study presents evidence regarding preliminary validation of a novel brief questionnaire, the Functional Seizures Pre-Post Intervention Comparison Survey (FSPICS) designed to measure patient relevant metrics following treatment.

Methods

Exploratory and confirmatory factor analyses were conducted to assess the latent structure of the FSPICS. Spearman’s correlation coefficients were used to estimate the association between relevant FSPICS questionnaire items and changes in monthly seizure count, Short Form-12 (SF-12) physical and mental quality of life component summaries, as well as the Work and Social Adjustment Scale (WSAS) function measure.

Results

A total of 56 participants enrolled in the active treatment arms of a Randomised Controlled Trial who completed the FSPICS were included. The final 19-item FSPICS assessed perceived treatment effectiveness across two highly correlated latent factors (r = 0.880), “Seizure Control” and “Quality of Life”. The final model exhibited overall very good fit (CFI = 0.999, TLI = 0.999, SRMR = 0.085, RMSEA = 0.034) and had strong internal consistency and reliability for both latent factors (“Seizure Control”: Ordinal Cronbach’s α = 0.957, McDonald’s ω = 0.929; “Quality of Life”: α = 0.913, ω = 0.867). Q12 of the FSPICS, “seizure occurrence”, demonstrated significant moderate-to-strong correlations with both absolute change in monthly seizure count (Spearman’s ρ = -0.514, p < 0.001) and seizure count ratio (Spearman’s ρ = −0.644, p < 0.001). Q9, “the strategies I use to manage my seizures help me function better in everyday life” and Q13, “quality of life” showed significant weak correlations (Spearman’s ρ = 0.362, p = 0.006 and Spearman’s ρ = 0.286, p = 0.032 respectively) with the change in the WSAS functional impairment score.

Conclusion

This study provides encouraging evidence of the FSPIC’s capacity to assess patient-reported outcomes and experiences of functional seizure treatment within a single brief questionnaire. Future studies with larger external sample sizes are required to further validate these findings.