External validation of the Memory Assessment Clinics Scale for Epilepsy (MAC-E)

Objective: This study aimed to externally validate the Memory Assessment Clinics Scale for Epilepsy (MAC-E), a brief self-report measure of subjective memory complaints in adults with epilepsy. Methods: A cross-sectional study was conducted including adults with focal pharmacoresistant epilepsy from three Level 4 epilepsy centers in the U.S., who completed the MAC-E as part of a clinical neuropsychological evaluation. Confirmatory factor analysis was conducted, and goodness-of-fit criteria were calculated to assess model fit: comparative fit index (CFI), root mean square error of approximation (RMSEA), and standardized root mean residual (SRMR). Item response theory models were constructed, and Mokken analysis was used to assess discrimination and unidimensionality. Internal consistency was evaluated with McDonald's Omega. Results: There were 191 patients included in the study (mean age = 41 ± 14, 51 % female, 87 % white race). Confirmatory factor analysis supported the 5-factor structure of the MAC-E identified in prior research (CFI = 0.989, RMSEA = 0.056, SRMR = 0.069) with high standardized loadings and R² values for each of the 5 factors (0.58–0.91 and 0.34–0.82, respectively). MAC-E items demonstrated high levels of discrimination as well as the ability to evaluate across the entirety of each latent trait. Score responses were uniformly distributed across latent traits, and unidimensionality was established by factor (all H coefficients > 0.4). Internal consistency was high across factors (omega range: 0.77–0.88). Conclusions: Results of this study demonstrate good external validation of the MAC-E in an independent, multicenter cohort of adults with epilepsy. These findings provide further support that the MAC-E is a psychometrically valid, self-report instrument to assess every-day memory abilities in adults with epilepsy in both clinical and research settings.