Table 1 Defining “pre-symptomatic” and “very high likelihood”

Pre-symptomatic

• This work emphasizes the development of intervention prior to 12 months of age, before the consolidation of symptoms into a diagnosable disorder.

• The term “pre-symptomatic” is used throughout the manuscript to refer to the postnatal period until ~ 12 months of age—a period when no or very few symptoms of ASD are present, and symptoms have not consolidated into a diagnosable disorder (ASD).

• Alternative terminology, including “pre-diagnosis”, “pre-emptive”, “pre-syndromic”, and “prodromal” was considered, though these options were eliminated as none was considered a better option with respect to criteria of accuracy, specificity, and conventionality.

Very high likelihood (VHL)

• High likelihood (HL) is defined by the increased likelihood of a later ASD diagnosis based on one “risk” marker, such as having a sibling with ASD.

• Very high likelihood of ASD (VHL-ASD) refers to a combination of “risk” markers: such as predictive brain markers and a sibling with a diagnosis of ASD. Defining VHL-ASD may be expanded to include other combinations of markers as research advances in its accuracy and reproducibility of predicting later ASD.

• The term “likelihood” is used throughout, though “risk” has been used in prior empirical work. Further discussion within the field surrounding the use of this term is necessary [14].

• Developing a framework for pre-symptomatic intervention in VHL-ASD infants is the primary focus of this work as it holds great importance to the field and relevance to a significant number of families with children born after the birth of an autistic child.

• In the future, this work can be extended to the general population of autistic children, though to date, biomarkers have not been identified to make this currently possible.