Harold L. Doherty recently posted a link on Twitter to a study on the usefulness of the diagnostic criteria for autism in children with intellectual disabilities. The study was published in the June, 2010 issue of Focus on Autism and Other Developmental Disabilities.
The study tested 89 children with intellectual disabilities on a variety of tests, including for intelligence, adaptive behavior, and language ability. Then, children were assessed for autism using the ADOS-G, an observation scale for autistic behaviors. A consensus was reached over whether they had ASD (31 children) or not (58 children). Then, a parent of each of the children was given a semi-structured interview based on DSM-IV-TR criteria for autism. The resutls of these interviews were than analyzed to determine which criteria each child met. This information was used to determine the sensitivity (how likely this criterion was to correctly identify children with ASD) and specificity (how well this criterion correctly identified children without ASD as such) for each criterion. Differences in which criteria were met, could not be explained by differences in IQ, adaptive behavior, or any other independent variable, since there were no significant differences between groups on these measures. That is interesitng in itself, but not the focus here.
It was found that all four criteria of the social interaction domain (poor non-verbal communication, lack of appropriate peer relationships, lack of spontaneous sharing, and lack of social and emotional reciprocity), two of the criteria of the communication domain (stereotyped language and lack of appropriate make-believe play), and one of the criteria of the stereotypic behavior domain (stereotyped or restricted interests) were useful in distinguishing children with intellectual disability and ASD from those with only an intellectual disability. Within the domain of social interaction, an impairment in non-verbal communication was the most useful criterion, with both pretty good sensitivity and specificity. Interestingly, only impairment in non-verbal communication and stereotyped language have both sensitivity and specificity greater than 70%. The reason for the lack of usefulness of the other criteria was mostly the fact that a significant number (over forty percent, often) of the children with only intellectual disability and no ASD, also met these criteria. Interestingly, only 33% of the children who had ASD, met the criterion of preoccupation with parts of objects. This makes me wonder how useful this criterion is in the diagnosis of autism in general. It is not being proposed as a criterion in DSM-V anymore.
As I said, DSM-IV-TR interviews were used in this study. The authors stress the importance of using an observational method for diagnosing ASD in children with intellectual disabilities. They also advise that further research be done into specific methods of diagnosing autism in individuals with intellectual disability. Besides the fact that, apparently, only half the DSM-IV-TR criteria are useful in diagnosing ASD in people with intellectual disabilities, the reasoning goes that it is possible that, on the other criteria, there may be qualitative and quantitative differences between people with intellectual disabiliteis with and without ASD. These qualitative or quantitative differences are not properly identified by an all-or-nothing algorithm such as the DSM.
Lastly, research is needed on the usefulness of autism diagnostic criteria for people without intellectual disabilities versus those who do have intellectual disabilities. After all, the authors say, it is possible that autism presentation varies depending on level of intellectual ability. I would say that such research could also help us further figure out the complex interrelatedness between cognitive, social, behavioral, and communicative impairments that is seen in both autism and intellectual disability, and in the combination of these.
Hartley SL, Sikora DM (2010), Detecting Autism Spectrum Disorder in Children With Intellectual Disability: Which DSM-IV-TR Criteria Are Most Useful? Focus on Autism and Other Developmentqal Disabilities, 25(2):85-97. DOI: 10.1177/1088357609356094.
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