Development and initial validation of the Communication Inventory Disability – Observer Reported (CID-OR): a measure of communication in CDKL5 deficiency disorder

CDKL5 Deficiency Disorder (CDD) is a rare neurodevelopmental disorder characterised by early onset seizures combined with complex healthcare needs and developmental impairment that influence functional domains including communication. Communication is a high priority domain for families but currently used measures demonstrate floor effects. Emerging disease-modifying trials necessitate the precise and granular measurement of communication to determine drug efficacy. This study evaluated a new measure of communication for CDD called the Communication Inventory Disability – Observer Reported (CID-OR). CID-OR was developed using a communication framework for CDD created from qualitative data and informed through evaluation of current measures and consultation with clinical experts. Scores for items describing communicative purpose were derived from ratings of consistency and the mode of delivery. An online survey was administered to parents of people with CDD (n = 184) recruited from the International CDKL5 Clinical Research Network. Most caregivers (96%) completed the Communication and Symbolic Behavior Scales - Developmental Profile Infant Toddler Checklist (CSBS–DP ITC). A confirmatory factor analysis was conducted. Test-retest reliability and comparison of known groups were assessed using intraclass correlation coefficients and linear regression, respectively. The median age of people with CDD was 9.8 (1–43) years. A single factor model was evaluated. For 34 items, item loadings were satisfactory. For the scale, internal consistency and goodness-of-fit statistics were satisfactory, except for the Root Mean Square Error of Approximation statistic. The distribution of CID-OR scores was less right skewed than for CSBS-DP ITC scores although there was a high correlation between CID-OR and CSBS scores (r = 0.89). Test-retest reliability was high (ICC 0.966). Preliminary analysis suggests that CID-OR is a reliable and valid measure of communication in CDD. This new tool has strong potential to measure responsiveness to interventions in CDD and may extend to similar developmental and epileptic encephalopathy conditions.