Prevalence of Autism Spectrum Disorder (ASD) in all Individuals Diagnosed with Down Syndrome (DS): A Systematic Review and Meta-analysis Protocol

Traditionally, autism spectrum disorder in people with Down syndrome was believed to be uncommon. This misconception is rooted in the challenges that a dual diagnosis poses. In fact, evidence indicates that children with Down syndrome are at risk for autism spectrum disorder with a potentially higher prevalence than the typically developing population. The purpose of this review is to determine the reported prevalence rate of autism spectrum disorder in all individuals with Down syndrome in comparison to the prevalence rate of autism spectrum disorder in the typical population when speci�c diagnostic tools are used. We will conduct a systematic review of the prevalence and incidence data and perform a meta-analysis on these results. This study will consider all studies that reported on children and adults with an existing diagnosis of Down syndrome and diagnosed by the standardized assessments for autism spectrum disorder. We will also consider the diagnoses made by team assessment (psychologist, psychiatrist & developmental pediatrician), according to DSM-III, DSM-IV or DSM-V criteria for diagnosing autism spectrum disorder or if they use autism spectrum disorder screeners. Studies will be considered from all countries that have data reporting prevalence on this topic. We will not apply language restrictions, attempting to translate studies that are not in English. We will search �ve databases (MEDLINE, Embase, PsychINFO, Scopus, and CINAHL). Two reviewers will conduct all screening and data extraction independently. The articles will be categorized according to key �ndings and a critical appraisal performed. The results of this review will bring increased awareness of the presence of autism spectrum disorder in individuals with Down syndrome. In doing so, this may facilitate a recommendation for screening and diagnosis for autism spectrum disorder in all individuals with Down syndrome. Based on the research demonstrating the bene�ts of early identi�cation and intervention on the outcomes of children with autism, we anticipate similar bene�ts in this population. This will guide the allocation of resources and direct future research. ASD, ASQ, Autism Screening Questionnaire; ASS-Q, Asperger Screening Questionnaire; Scale; CSBS-DPDS, Communication and Symbolic Behavior Scales Developmental Pro�le; DBC-ASA, Developmental Checklist-Autism Screening DBC-ES, Developmental Checklist-Early Diagnostic Social and Communication Disorder; Down syndrome; DSM, Diagnostic and Statistical Manual of Mental Disorders; DSMIG, DS, Down Down Syndrome GARS-2, Gilliam Autism – HBS, and Skills ICD-10, Classi�cation of Diseases-10; Intellectual disability; Modi�ed Checklist for Autism in Toddlers – Revised; PEDS, Parents’ Evaluation of Developmental POSI, Parent’s Observations of Social Interactions; PCC, Population, Concept, Context; PRISMA-P, Preferred Reporting Items for Systematic Reviews and Meta-analysis for Protocols (PRISMA-P) guidelines; RITA-T, Rapid Interactive Screening Test for Autism in Toddlers; Social Communication Questionnaire; SRS, Social Responsiveness Scale; STAT, Screening Tool Autism Young Children.