Cameron Jackson DrCameronJackson@gmail.com
Some caveats concerning the use of the ADOS in the assessment of autism.
One caveat: The ADOS measures autistic spectrum disorders but does not distinguish between the severity of autistic symptoms. That is, it does not distinguish between 299.0 Autistic Disorder (most severe), PDD-NOS (less severe) and Asperger’s Disorder (normal IQ and normal adaptive functioning).
A second caveat: The ADOS only picks up information between the interaction of an adult (psychologist, therapist) with a child. Unfortunately, there is no sampling of the child’s behaviors with same age peers. And, needless to say, how a child interacts with same age peers is crucial information. Frequently persons with an autistic spectrum disorder (ASD) do fine with persons older or younger. How the ASD functions in relation to persons fairly close in age is highly important. Why? In America, we educate children that are the same age. In many states, including California, once a child has been held back one time they cannot be held back again. So if a child cannot readily function with same age peers that is highly significant for that child’s educational experience.
The ADOS, a measure of autistic spectrum disorders, is a very different kind of measure compared to measures of intelligence.
We have lots of measures of intelligence and they all do a fairly good job. Most of the well known measures of intelligence result in standard scores and persons can be classified in a range: Average range, Superior range, Deficient range. A person who scores in the Average range on one measure typically and usually will score in the Average range on other measures of intelligence. For example, the Test of Nonverbal Intelligence (TONI) will give a standard score in the Average range that is fairly close to the Performance I.Q. of a Wechsler IQ test.
In contrast to measures of intelligence (I.Q.), the measurement of autistic spectrum disorders with an ADOS does not result in a standard scores. Scores are not spread out along the bell curve. Thus it is mot possible to talk about Average range, Superior range, Deficient range.
Hence, because there are no standard scores there is no way to compare performance on the ADOS with all the hundreds of tests that exist which use standard scores.
Instead of providing standard score information, the ADOS has a “cut-off” score. If the person scores above then they supposedly have an autistic spectrum disorder. The ADOS does include Category 3 (repetitive behaviors, unusually strong, limited interests) items in determining the overall scores.
So what happened to the ADOS for toddlers that was coming soon — but not here yet?
How did the new ADOS Module T perform?
1.The sensitivity of the ADOS Toddler module was 91%. That is, the test was able to correctly identify 91% of the cases of ASD (based on a cut off score of 12).
2.The specificity of the ADOS-Module T when tested against non-ASD disorders was also 91%. This means that only in 9% of the cases, the test suggested a diagnosis when the child had been previously identified as not having an ASD.
3.The specificity of the ADOS-Module T when tested against typically developing cases was 94%. That is, only in 6% of the cases, the test suggested a diagnosis in children who were actually typically developing kids.
What happened to the ADOS Toddler Module? Not happening?
One of the authors writes:
“These are actually excellent numbers and indicate that the ADOS Toddler Module has excellent sensitivity and specificity. However, the authors also described some general concerns and limitations.
The ADOS, although it is the most reliable and valid diagnostic instrument available, it is still only a clinical tool that must be used in the context of a comprehensive clinical evaluation and it is subservient to clinical judgment.
Specifically, a diagnosis of autism is provided only when the person meets the DSM-IV diagnostic criteria. Therefore, clinicians must use their judgments in interpreting and applying the results from the ADOS. There will be cases when the ADOS suggests a diagnosis but the clinician will not provide the diagnosis because the child doesn’t meet full diagnostic criteria based on the DSM-IV.
So you may ask, what is the point? Why do we have the ADOS if all a clinician has to do is go down the list of the DSM-IV criteria and add up the check marks? The ADOS provides for a reliable and valid tool to assess for the specific symptoms included in the DSM-IV criteria and it helps the clinician interpret the child’s clinical presentation as it applies to the DSM-IV criteria. The ADOS standardizes this process so that diagnoses are less dependent upon other factors, such as biases in parental reporting of symptoms, or the skills or training of the clinician in properly indentifying such symptoms. Therefore, the ADOS greatly improves the validity and accuracy of our ‘clinical judgment’.
On a personal note and disclaimer. Dr. Luyster (lead author of the study), Dr. Richler, and Dr. Oti were all my classmates in graduate school and I congratulate them for their wonderful work. In addition Dr. Lord, creator of the ADOS and founder of the University of Michigan Autism and Communication Disorders Clinic, will be my collague this Fall when I join the University of Michigan faculty.
The Reference: Luyster, R., Gotham, K., Guthrie, W., Coffing, M., Petrak, R., Pierce, K., Bishop, S., Esler, A., Hus, V., Oti, R., Richler, J., Risi, S., & Lord, C. (2009). The Autism Diagnostic Observation Schedule—Toddler Module: A New Module of a Standardized Diagnostic Measure for Autism Spectrum Disorders Journal of Autism and Developmental Disorders DOI: 10.1007/s10803-009-0746-z
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