Validation of the Observer-Reported Communication Ability (ORCA) measure for individuals with Rett syndrome.

PURPOSE:The study goal was to validate the Observer-Reported Communication Ability (ORCA) measure for use with females with Rett Syndrome (RTT). METHODS:Qualitative interviews, including concept elicitation and cognitive interviewing methods, were conducted with 19 caregivers of individuals with RTT ages 2 and older. A quantitative study was then conducted in 279 caregivers to evaluate construct validity and reliability. RESULTS:After minor modifications were made, the modified ORCA measure was well understood and captured key communication concepts. Quantitative data showed evidence for reliable scores (α = 0.90, test-retest intraclass correlation = 0.88), minimal floor and no ceiling effects, and strong correlation with the Communication and Symbolic Behaviors Scale (r = 0.73). CONCLUSIONS:This study provided initial support that the modified ORCA measure is an acceptable caregiver-reported measure of communication ability for females with RTT. Future work should include evaluation of longitudinal validity of the measure and its associations with clinician- and performance-based measures in diverse samples.