Abstract
The Autism Observation Scale for Infants (AOSI) is being applied to non infant sibling populations. Assessment of the tool's utility across increased likelihood (IL) populations is therefore needed. A systematic review and meta-analysis was conducted on 17 studies identified from six databases. The AOSI has been used in four IL contexts: infant siblings, infants with Fragile X Syndrome, Tuberous Sclerosis Complex, and Down Syndrome. There were three main findings: (1) five studies report classification data though no consistent approach was used; (2) group differences between IL-ASD, IL non-ASD, and controls started at 12-months; and (3) large effect sizes between IL-ASD and control samples was identified. Utility of the AOSI to identify early signs of ASD in IL populations was demonstrated. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40489-023-00417-y.