The Gilliam Autism Rating Scale, now in its third edition, is one of the most widely used instruments for the assessment of Autism Spectrum Disorder in the world. The GARS-3 assists teachers, parents, and clinicians in identifying autism in individuals and estimating its severity. Items on the GARS-3 are based on the 2013 diagnostic criteria for autism spectrum disorder adopted by the APA and published in the Diagnostic and Statistical Manual of Mental Disorders–Fifth Edition (DSM-5). The GARS-3 yields standard scores, percentile ranks, severity level, and probability of Autism.
The instrument consists of 56 clearly stated items describing the characteristic behaviours of persons with autism. The items are grouped into six subscales: Restrictive/Repetitive Behaviors, Social Interaction, Social Communication, Emotional Responses, Cognitive Style, and Maladaptive Speech.