Can the AOSI at Nine Months Discriminate Between Infants at High or Low Risk for ASD?

Background: Recently, an important focus of longitudinal research has been to isolate specific risk markers that are present in the first year of life, long before a confirmed ASD diagnosis is typically given. As a result of this body of early risk research, the Autism Observation Scale for Infants (AOSI) was developed by Bryson and her colleagues (Bryson, Zwaigenbaum, McDermott, Rombough, & Brian, 2007). The AOSI has the ability to identify infants who are later diagnosed with autism from other low risk controls as early as twelve months (Zwaigenbaum et al., 2005); however, at 6 months, AOSI scores do not predict later diagnostic outcomes. It is not yet known whether AOSI scores in infants younger than twelve months can be used to predict later ASD symptoms.

Objectives: The objective was to determine whether differences in infants at high (HRA; defined as infants with an older sibling with an ASD diagnosis) versus low risk (LRC) for ASD are evident as early as nine months for scores on the AOSI regardless of outcome. Furthermore, to investigate whether AOSI scores at nine months predict ASD symptoms at eighteen months, as measured on the Autism Diagnostic Observation Schedule (ADOS), independent of risk group. 

Methods: The AOSI  was administered to HRA (n=32)  and LRC infants (n=31) at nine months  and HRA infants (n=71) and LRC infants (n=43) at twelve months as a part of their participation in the Infant Sibling Project taking place at Boston University and Children’s Hospital. A total of 42 infants (HRA n=26; LRC n= 16) were administered the AOSI at both ages. At eighteen months, the (ADOS) was administered to all infants enrolled in the study to determine a preliminary outcome.

Results: Independent samples t-test confirmed significant differences found by Zwaigenbaum et al. in total AOSI scores at twelve months for HRA infants (M=3.86, SD=2.914) and LRC infants (M=2.16, SD=2.137); t(112)=-3.313, p<.01. A significant difference was also found in total nine month AOSI scores for HRA infants (M=4.91, SD=3.073) and LRC infants (M=3, SD=1.265); t(61)=-3.201, p<.01. Furthermore, an additional independent samples t-test removing infants who received a preliminary ASD outcome (based on meeting cutoff scores on the ADOS at 18 months) still revealed significant group differences between nine month AOSI total scores and group with HRA infants performing significantly poorer on the AOSI (M=4.84, SD=3.099) than LRC infants (M=3, SD=1.265); t(60)=-3.058, p=<.01. Nine month AOSI scores did not, however, predict scores on any of the subscales of the ADOS.

Conclusions: These findings suggest that high risk infants show differences on the AOSI at nine months. Further analyses will investigate whether specific items of the AOSI (such as response to name, atypical eye contact, social smiling, etc.) can predict ADOS scores at eighteen months.