Evaluating Validity of the Autism Observation Scale for Infants (AOSI) Among Infants Identified with Possible Autism By Community Care Professionals
Objectives: To conduct an independent evaluation of validity of the AOSI in a community-referred sample.
Methods: Infants aged 9-16 months (n=103; 68% boys) were referred due to showing early signs of autism according to the Social Attention and Communication Surveillance (SACS) protocol (Barbaro & Dissanayake, 2010). Specifically, all infants showed ≥3 (of 5) key markers on the SACS 12-month checklist (i.e., absent/atypical eye-contact, response to name, imitation, pointing, other gestures). Infants attended two assessments, 6-months apart. We administered the AOSI, Mullen Scales of Early Learning (MSEL) and Vineland Adaptive Behavior Scales (VABS) at Time 1 (T1) and Time 2 (T2), with the Autism Diagnostic Observation Schedule–Toddler Module (ADOS-T) also administered at the latter. AOSI assessments were coded live and from video, with 20% of tapes double-coded.
Results: Very high agreement was observed for live vs. video scoring of T1 AOSIs (within-rater live/video agreement on 100% assessments, r=.89; inter-rater agreement on 20% tapes, r=.79). At both T1 and T2, AOSI Total scores approximated a normal distribution, centred on the previously-reported threshold score of 9 (T1: M=9.44, SD=4.05; T2: M=9.32, SD=4.68). At T1, AOSI scores were significantly – though only weakly – associated with concurrent MSEL (r= -.23, p=.017) and VABS totals (r= -.23, p=.023), but were elevated among children with ≥4+ (vs. only 3) SACS markers at referral (F[2,102]=6.73, p=.002). At T2, AOSI scores were moderately associated with MSEL (r= -.36, p<.001) and VABS totals (r= -.43, p<.001), and more strongly associated with ADOS-T Algorithm totals (r=.627, p<.001). AOSI scores showed only moderate T1-T2 association/stability (r=.441, p<.001) and T1 AOSI scores only moderately predicted T2 ADOS-T totals (r=.412, p<.001).
Conclusions: The AOSI is reliably scored and shows some validity for quantifying autism behaviours in a community-referred sample of infants. We observed an approximately normal distribution of AOSI scores in our sample – centred on the previously suggested threshold for likely later diagnosis – but with only moderate/weak within-participant stability over time. Like ‘high-risk siblings’, community-referred infants with early signs of autism may experience variable trajectories of early development. The high-level reliability of video (vs. standard/live) ratings supports the AOSI as a viable measure for inclusion in protocols necessitating blinded evaluation; for example, as a primary outcome measure for pre-emptive intervention trials.