Reliability and Factor Structure of the Autism Spectrum Disorders—Diagnosis Scale for Intellectually Disabled Adults (ASD—DA)

Most of the scale development work in autism spectrum disorders (ASD) to date has focused on instrumentation designed for one disorder, autism, and mainly focused on young children. Three hundred seventy-one staff were administered a newly developed assessment scale for adults with ID. The Autism Spectrum Disorders—Diagnosis Scale for Intellectually Disabled Adults (ASD—DA) was designed to quickly provide relevant information to establish a diagnosis for the most common ASD (autism, PDD-NOS, and Asperger’s syndrome). Staff completed the assessment for adults with ID (n = 192) some of which had a diagnosis of either autism or PDD-NOS (n = 107) or ID alone (n = 85). Inter-rater and test-retest reliability data were obtained. Item analysis reduced the scale to 31 items that were found to be both reliable and significantly differentiate between groups. A factor analysis with a three-factor solution was identified. The internal consistency of factor and total scale scores were found to be excellent.