101 Detecting Early Behavioural Markers of Autism in High-Risk Infants

To better inform early identification efforts, we have initiated a prospective study of high-risk infants, defined as such by having an older sibling with autism (hereafter, ‘siblings’). Our main goal is to assess whether behavioural markers in the first year of life can identify which children are most likely to receive a subsequent diagnosis of autism.

We have operationalized behavioual risk markers for autism hypothesized from previous research and have developed a standardized procedure for detecting these markers within a brief observational assessment, the 18-item Autism Observation Scale for Infants (AOSI). The test-retest and inter-observer reliability of the AOSI at 12 months are good (intraclass correlation 0.66 and 0.92 respectively). AOSI risk markers observed at 12 months in siblings and low-risk controls were assessed in relation to diagnostic classification at 24 months of age as determined independently by the Autism Diagnostic Observation Scale (ADOS).

Our current sample includes 65 siblings and 23 control infants who have been followed from 12 months to at least 24 months of age. 24-month ADOS scores exceed threshold for autism in 7 siblings (all of whom have subsequently received clinical diagnoses based on DSM-IV criteria), and exceed threshold for ‘autism spectrum disorder’ (ASD) in an additional 13 siblings (2 of whom have received clinical diagnoses). The number of risk markers observed at 12 months predicts ADOS classification at 24 months, based on 1-way ANOVA (F3,84=25.4; p<.001). Siblings with an ADOS classification of autism at 24-months had a mean of 8.1 markers (SD=2.7) at 12-months, compared to a mean of 4.0 markers in siblings classified with ASD (SD=2.2); siblings and controls scoring below ASD threshold at 24-months had a mean of 2.1 markers (SD=1.9) and 1.5 markers (SD=1.6) at 12-months, respectively. Post-hoc analyses indicate significant differences between the autism, ASD, and non-ASD subgroup means. Individual 12-month AOSI risk markers that predict autism at 24 months include atypical eye contact, visual tracking, disengagement of visual attention, orienting to name, imitation, social smiling, reactivity, social interest, and sensory-oriented behaviour (all p<.003 to adjust for multiple comparisons).

Early signs of autism can be identified prospectively in high-risk infants within a brief but systematic clinical assessment at 12 months of age. Additional follow-up and outcome assessment of this unique high-risk sample, as well as evaluation of these risk markers in other high- and low-risk samples will be needed to determine the sensitivity and specificity of these markers for autism.