What is the ADOS?

The Autism Diagnostic Observation Schedule (ADOS) is the “gold standard” for diagnosing autism spectrum disorders including pervasive developmental disorder (PDD) and Asperger’s Syndrome--or ruling them out--at any age and developmental level, irrespective of language skill or level of functioning. It can be quickly and reliably administered to subjects ranging from children as young as 18 months old through adolescence and adulthood.

In widespread use in research and in academic centers, the ADOS has quickly become the leading tool used by clinicians when an autism spectrum disorder is suspected. It is flexible, fast, accurate and extraordinarily useful. One researcher calls it, “the best and most comprehensive autism assessment in the world.”

The ADOS assesses behavior, communication, social interaction, play and the imaginative use of materials for individuals suspected of having autism or other related disorders. It consists of four modules, each attuned to differing developmental and language levels, ranging from little if any expressive or receptive language, as in toddlers, to verbally fluent adults. Each module takes just 30-45 minutes to administer.

Here’s how University of Michigan Professor Catherine Lord, Ph.D., principal author of the ADOS, describes its use in practice with children: “The interviewer selects which module to use based upon the age of the child and how well he or she can talk. Each module consists of about ten tasks that are designed to evoke different kinds of social behaviors, such as sharing and requesting, playing with someone and following, and enjoying attention. The test can be performed in not much more than half an hour during an office visit as part of the diagnosis. The idea is that to make a diagnosis, information from parents, because they know the child better than any clinician or researcher, should be combined with the observations of the clinician.”

To gather that information from parents, and to help them reflect upon and structure their thoughts, the clinician may engage with them using another potent instrument, the Autism Diagnostic Interview (Revised), or ADI-R. When used together, these tests yield the most accurate assessments of autism spectrum disorders currently available.

Why does NESCA use the ADOS?

• The ADOS is reliable, fast, efficient and, because it’s play-based, fun for small children. For all involved, it’s less stressful than other tests;
• The ADOS has exceptional sensitivity and specificity. These are terms used by researchers to evaluate the accuracy of test results.
  
  Sensitivity refers to how accurate instruments are in correctly identifying, where they actually exist, the conditions they were designed to detect. As reported last year at IMFAR, the International Meeting for Autism Research, the latest version of the ADOS achieved a sensitivity rating of 95%, meaning that ADOS testing would yield a correct diagnosis 95% of the time. Only 5% of test administrations would yield “false negatives” in which autism spectrum disorders are missed, resulting in unfortunate delays in the onset of intervention and treatment.
  
  Many other tests commonly used to assess autism spectrum disorders in toddlers, including some of the most highly-regarded, are significantly less sensitive than the ADOS. For example, the Checklist for Autism in Toddlers, or CHAT, and the Early Screening for Autistic Traits, or ESAT, miss as many of 50% of cases later correctly diagnosed, even when administered by experts.
  
  Specificity relates to how well a test differentiates its target condition from others that may be present. Again, the ADOS was found to have an extremely high specificity of 95%. This means that test subjects with symptoms perhaps resembling autism but with other underlying causes will be misdiagnosed only about 5% of the time. In other words, there are far fewer “false positives” than with other tests. Confident that autism spectrum disorders are not involved, parents could then seek out other, correct explanations for their children’s behavior and/or academic difficulties.
  
  As Dr. Catherine Lord explains, the ADOS defines the “boundary between autism spectrum disorder and milder disorders with overlapping symptoms, like ADHD, nonverbal learning disability and speech and language problems.”
  
  It is very unusual for tests to have such high sensitivity and specificity. No wonder Leading Autism Researcher Nestor Lopez-Duran, Ph.D. calls the ADOS “the most reliable and valid diagnostic instrument available.”
  
  
• Closely related to sensitivity is the statistical concept of internal validity, which has been established for the ADOS. This means that clear causal links have been shown to exist between autism spectrum disorders and the traits identified by the test. The ADOS also displays a high level of test-retest reliability, because it will yield the same results in repeated administrations over time.
• The ADOS has demonstrated very high inter-rater reliability, exceeding 84%. This means that two or more trained testers observing the same child but scoring independently will reach the same conclusions more than 84% of the time. This is significant because sometimes, test results may be influenced by extraneous factors including where and when a test is given, the child’s emotional state, his or her rapport with the person giving the test and that clinician’s subjective impressions of the child. The ADOS offers greater objectivity than most tests.

How has NESCA qualified its staff to administer the ADOS?

• Our entire clinical staff participated in two full days of professional training in administration of the ADOS. Offered as part of NESCA’s ongoing program of continuing education, the course was taught by Clinical Psychologist Rachel Hundley, Ph.D. of Harvard Medical School and Children’s Hospital Boston, where she is co-director of the Autism Care Program within the Division of Developmental Medicine. Specialized in the assessment of children with developmental difficulties as well as ongoing care for children with autism spectrum disorders, Dr. Hundley is a certified trainer for the Autism Diagnostic Observation Schedule and teaches the ADOS nationally and internationally.
• All of our clinicians are also training with a DVD-based program created by Western Psychological Services, publishers of the ADOS, in which they are required to score, as if they had administered the tests themselves, several videotaped ADOS testing sessions with actual subjects of differing ages and abilities. This assures their fluency with all four test modules. Their scoring protocols and notes will be submitted to WPS for validation. If their findings are accurate and consistent with those of the WPS-certified trainers grading their performance, each will be awarded 18 Continuing Education Units recognized by the State of Massachusetts. NESCA will require that they re-use these and other educational materials periodically to maintain their proficiency.
• NESCA is supporting one of our clinicians, John Goodson, in his efforts to achieve research-level certification as an ADOS tester. Research training focuses on bringing an individual’s scoring skills to a high level of inter-rater agreement with the scoring practices of highly-experienced examiners. The heightened level of accuracy is needed to ensure that item-level coding is comparable at different labs in different parts of the world where research is being conducted. He will attend courses conducted at the university laboratory of one of the test authors.
  
  Having completed both the ADOS clinical workshop conducted by Dr. Hundley and the ADOS research training, achieving accuracy consistent with the research workshop team, he will be able to supervise our staff and offer in-house training.

What is the ADI-R?

The Autism Diagnostic Interview-Revised (ADI-R) is another excellent diagnostic instrument for assessing autism spectrum disorders in children and adults. This parental interview, which typically can be completed in about 90 minutes, consists of 93 items and focuses on behaviors in three content areas: quality of reciprocal social interaction, communication and language, and repetitive, restricted and/or stereotyped interests and behaviors. It also includes questions about other issues relevant for treatment planning, such as self-injurious behavior and over-activity.

Responses are scored by the clinician based on the caregiver’s description of the subject’s behavior. Questions are grouped within content areas, and definitions of all behavioral items are provided. The ADI-R interview generates scores in each of the three content domains (i.e., communication and language, social interaction, and restricted, repetitive behaviors). An elevated score indicates problems in a particular area. A classification of autism is given when scores in all three content areas meet or exceed specified cutoffs, and onset of the disorder is evident by 36 months of age. The same algorithm is used for subjects from mental ages 18 months through adulthood.

High levels of inter-rater and test-retest reliability, as well as internal validity, have also been demonstrated for the ADI-R. We often use it at NESCA in concert with the ADOS in recognition of the fact that over time, parents become the foremost authorities on their child’s behavior in a variety of circumstances and social contexts.