Multidimensional Influences on Autism Symptom Measures: Implications for Use in Etiological Research

Abstract

Objective: Growing awareness that symptoms of autism spectrum disorder (ASD) transcend multiple diagnostic categories, and major advances in the identification of genetic syndromes associated with ASD, have led to widespread use of ASD symptom measures in etiologic studies of neurodevelopmental disorders. Insufficient consideration of potentially confounding factors such as cognitive ability or behavior problems can have important negative consequences in interpretation of findings, including erroneous estimation of associations between ASD and etiologic factors.

Method: Participants were 388 children 2 to 13 years old with diagnoses of ASD or another neurodevelopmental disorder without ASD. Receiver operating characteristics methods were used to assess the influence of IQ and emotional and behavioral problems on the discriminative ability of 3 widely used ASD symptom measures: the Social Responsiveness Scale (SRS), the Autism Diagnostic Interview-Revised (ADI-R), and the Autism Diagnostic Observation Schedule (ADOS).

Results: IQ influenced the discriminative thresholds of the SRS and ADI-R, and emotional and behavioral problems affected the discriminative thresholds of the SRS, ADI-R, and ADOS. This resulted in low specificity of ASD cutoffs on the SRS and ADI-R for children with intellectual disability without ASD (27-42%) and low specificity across all 3 instruments for children without ASD with increased emotional and behavioral problems (36-59%). Adjustment for these characteristics resulted in improved discriminative ability for all of the ASD measures.

Conclusion: The findings indicate that scores on ASD symptom measures reflect far more than ASD symptoms. Valid interpretation of scores on these measures requires steps to account for the influences of IQ and emotional and behavioral problems.

Keywords: Autism Diagnostic Interview–Revised; Autism Diagnostic Observation Schedule; Social Responsiveness Scale; discriminative ability; measurement.

Figure 1

(A, B, C): Box-plot diagrams showing the distributions of autism symptom scores for children with and without autism spectrum disorder (ASD) by level of emotional/behavioral problems (EBP), and effect sizes of the mean differences between diagnostic groups (non-ASD versus ASD). Note: ASD=autism spectrum disorder, SRS=Social Responsiveness Scale, ADI=Autism Diagnostic Interview-Revised, ADOS=Autism Diagnostic Observation Schedule, Parent-rated EBP=Child Behavior Checklist Externalizing or Internalizing scale in clinical range (T≥64). Clinician-observed EBP=ADOS Other Abnormal Behaviors section. ES=effect size (partial eta squared),*p<0.05, ** p<0.01, *** p<0.001.