Diagnostic Differentiation of Autism Disorders and Pragmatic Language Impairment

Background: The diagnostic and clinical differentiation between children with autism spectrum disorders (ASDs) and children with pragmatic language impairment (PLI), two populations that share a similar linguistic profile, was examined in school-aged children.  Charting the behavioral and cognitive profiles of these populations can serve to aide diagnostic differentiation and educational intervention. Objectives: The objectives of this study were two-fold. One, to compare scores on diagnostic measures of autism between school-age children with ASD and those with PLI. Two, to investigate differences between children in these groups and typically developing children in the areas of social cognition and executive function. Methods: The participants included 22 school-aged children diagnosed with ASD (mean age = 10.2 years), 19 children with PLI (mean age = 9.6 years), and 35 typically developing comparisons (mean age = 10.5 years) matched on language age and IQ. All the participants were verbal and had an IQ above 80. In study 1, the participants with ASD and PLI were tested on the Autism Diagnostic Observation Schedule (ADOS) and the Social Communication Questionnaire (SCQ). In study 2, the participants in all three groups were tested on the measures of three hierarchical levels of Theory of Mind, a planning measure, and a response inhibition measure. Results: There was a significant difference between diagnostic groups in the level of severity of behaviors represented by the Communication and Reciprocal Social Interaction sub-domains on both diagnostic measures. However, in the sub-domain of repetitive and rigid behaviors, the difference between groups was subtler and not useful as a differentiating factor. While both the children with ASD and those with PLI violated more rules on the ‘planning in problem-solving’ task than the typically developing group, only the children in the ASD group demonstrated impaired functioning on the planning measure. The findings of this study suggest that children with PLI may be more vulnerable than children with ASD to developmental lags in understanding false belief but less vulnerable to impairments in planning and monitoring behavior. Conclusions: The diagnostic differentiation between ASD and PLI is complex, especially in school-age populations. Behavior symptoms may be more subdued in school-age children and thus should not be used as a tool for diagnostic differentiation. Social communication delays are generally more severe in children with ASD, with some children with PLI presenting with comparable levels of severity. Educational planning for these two populations must be informed by both group similarities (e.g. difficulty forming theories about the beliefs and desires of others in order to predict future behavior) and differences (e.g. planning in problem solving) in cognitive and social development. Thus, the development of individual education plans should be created within the general framework of known areas of strengths and weaknesses related to diagnostic categorization and then further tailored to childrens’ personal profiles based on an assessment of skills.