Abstracts

Rationale: Recently our team developed and assessed the psychometric properties of a shortened version of the Quality of Life in Childhood Epilepsy Questionnaire [QOLCE-55; Goodwin SW et al. (2015) Epilepsia doi:10.1111/epi.13000]. We continue our validation of the QOLCE-55 by rigorously evaluating whether the scale demonstrates measurement equivalence across age and gender in a large cohort of children with newly diagnosed epilepsy. Measurement equivalence concerns the extent to which the psychometric properties of observed scale items are generalizable across groups. Demonstrating measurement equivalence makes it possible to interpret differences between groups as real and meaningful. Without evaluating measurement equivalence, clinicians and researchers cannot be certain if observed differences reflect true differences or whether they are an artifact of differential interpretation of items or structure of the construct, in this case, health-related quality of life.Methods: Data come from the Health-Related Quality of Life in Children with Epilepsy Study (HERQULES), a multisite prospective cohort study of 373 children aged 4-12 years newly diagnosed with epilepsy. Multiple-group confirmatory factor analysis was used to examine the measurement equivalence of the QOLCE-55 in which a hierarchical set of equality constraints between (1) younger (4-7 years) and older (8-12 years) and (2) males and females was specified. Sequential testing occurred as follows: (i) configural invariance imposes no equality constraints on parameters; (ii) weak invariance (constrained factor loadings); (iii) strong invariance (constrained item thresholds/intercepts); and, (iv) strict invariance (constrained residual and factor variances). Evaluation of equivalence was determined by changes in the Comparative Fit Index (CFI) and Root Mean Square Error of Approximation (RMSEA) between sequential models. The following changes correspond to a relevant worsening of model fit: ΔCFI ≥-0.010; ΔRMSEA ≥0.015.Results: The analyzed sample had 179 younger and 181 older children; and, 191 male and 169 and female children (14 children were excluded due to completely missing data at the assessment). The QOLCE-55 demonstrated full measurement equivalence at the strict level for both the age [CFI=0.957, RMSEA=0.048 (0.045, 0.052)] and gender comparisons [CFI=0.956, RMSEA=0.048 (0.045, 0.051)]. Sequential results from the equivalence testing are shown in Table 1 and 2.Conclusions: The QOLCE-55 demonstrated full measurement equivalence at the strict level in a representative sample of children with newly diagnosed epilepsy. This suggests that any potential differences in scores between groups (younger vs. older; male vs. female) represent true differences and are not merely attributable to differences in the interpretation of items assessing health-related quality of life. The QOLCE-55 continues to demonstrate excellent psychometric properties and is a robust measure of health-related quality of life in children with epilepsy. HERQULES was funded by the Canadian Institutes for Health Research (MOP-64311).