Validating the Communication and Symbolic Behavior Scales–Developmental Profile Infant–Toddler Checklist (CSBS–DP ITC) Beyond Infancy in the CDKL5 Deficiency Disorder
Jacinta Saldaris, Helen Leonard, Kingsley J. H. Wong, Peter Jacoby, Mary Spence, Eric D. Marsh, Tim A. Benke, Scott Demarest, Jenny Downs
Abstract
CDKL5 deficiency disorder (CDD) results in early-onset epilepsy and lifelong cognitive and motor impairments. With no validated measure for communication in CDD, this study evaluated the psychometric properties of the Communication and Symbolic Behavior Scales-Developmental Profile Infant Toddler Checklist (CSBS-DP ITC). Caregivers (n = 150; affected individuals aged 1-29 years) completed the CSBS-DP ITC. Distribution of scores indicated a floor effect. There was poor divergent validity for the three-factor model but goodness of fit and convergent validity data were satisfactory for the one-factor model. Individuals with poorer overall functional abilities scored lower on the CSBS-DP ITC. Test-retest reliability was excellent. The floor effect could explain the very high reliability, suggesting problems as a sensitive outcome measure in clinical trials for CDD.