Sunday, January 15, 2012

Best Practice Review: The Autism Diagnostic Observation Schedule (ADOS)

One of the most widely used observation instruments for the assessment of autism is the Autism Diagnostic Observation Schedule (ADOS) (Lord, Rutter, DiLavore, & Risi, 2008). The ADOS is a semistructured assessment of social interaction, communication, play, and imaginative use of materials for individuals who may have autism or other autism spectrum disorder (ASD), also referred to as pervasive developmental disorder (PDD). The goal of the ADOS is to provide a hierarchy of “presses” (social structures) that elicit behaviors in standardized contexts relevant to ASD.
Use of the ADOS requires clinical training and practice in observation and scoring, as well as administering the standard activities. Clinical experience related to ASD and skill in working with children is recommended. It should be noted that the ADOS classification system does not assign a diagnosis. The ADOS has thresholds for social interaction, communication and communication-social interaction (total). An individual may reach the threshold on all three scales but not receive a clinical diagnosis of ASD, because of late presentation of difficulties or no restricted/repetitive behaviors or interests. The authors stress the importance of using the ADOS in conjunction with a developmental history, corroborating information from other sources, and the use of clinical judgment (Lord et al, 2008).
Administration and Scoring
The ADOS is standardized in terms of the materials used, the activities presented, the examiner’s introduction of activities, the hierarchical sequence of social presses provided by the examiner, and the way behaviors are coded or scored. The ADOS consists of four “modules,” each of which can be administered in 30-45 minutes. The appropriate module is selected and administered depending on the individual’s verbal ability. Module 1 is used for children who are preverbal or have single-word language. Module 2 is appropriate for individuals with phrase speech abilities. Module 3 is used for children and adolescents who are verbally fluent. Verbally fluent adolescents and adults are assessed with Module 4. More than one module can be administered if the examiner determines that a more or less advanced module is appropriate. The manual provides guidelines for selecting the most appropriate module and general instructions for administration and scoring and interpreting an individual’s results.
ADOS classifications are based on specific coded behaviors that are included in a scoring algorithm using the DSM-IV diagnostic criteria, resulting in a Communication score, a Reciprocal Social Interaction score, and a Total score (a sum of the Communication and Reciprocal Social Interactions scores). ADOS items regarding play and stereotyped behaviors are also coded but are not included in the diagnostic algorithm due to the difficulty in accurately assessing these characteristics in a limited period of time (Lord et al., 2008). Behaviors are coded using a 0- to 3-point coding system, with a 0 indicating that the behavior is not abnormal in the way specified in the coding description, 2 indicating a definite difference, and a 3 indicating that a behavior is abnormal and interferes in some way with the child’s functioning. Scores are compared with an algorithm cut-off score for autism or the more broadly defined ASD in each of these areas. If the child’s score meets or exceeds cut-offs in all three areas, they are considered to meet criteria for that classification on the measure. An ADOS autism classification requires meeting or exceeding each of the three thresholds (social, communication, social-communication total) for autism. If thresholds for autism are not met, an ADOS classification of ASD is appropriate when the three ASD thresholds are met or exceeded. In all cases, the ASD thresholds are lower for ASD than those of autism (Lord et al., 2001, 2008).
Psychometric Properties
The psychometric data used in the derivation of the diagnostic algorithms were obtained from individuals diagnosed with autism, pervasive developmental disorder not otherwise specified (PDD-NOS), and non-spectrum disorders in order to maximize diagnostic agreement. Individuals with a diagnosis of Asperger’s Disorder were not included in the validation sample (Lord et al., 2008). The manual provides a range of sensitivity and specificity data across modules for Autism and ASD vs. non-spectrum disorders. The instrument has sensitivity in the upper 90% range and specificity in the upper 80% to lower 90% range (Lord et al., 2008). The ADOS was very effective in discriminating individuals with either autism or ASD from those with non-spectrum disorders, while differentiation of autism and ASD resulted in specificities of .68 to .79. Agreement between raters for diagnostic classification when assessing individuals with autistic disorder, ASD, and non-spectrum disorders ranged from 81% to 93% for the four modules. Internal consistency for all domains and modules ranged from .47 to .94. The lower results were found for stereotyped behaviors and restricted interests in module 3. Test-retest reliability indicates excellent stability for the “Social Interaction” and “Communication” domains, and for their combined total, together with good stability for the “Stereotyped Behaviors and Restricted Interests” over an average period of nine months. In total, there seems to be significant evidence for sensitivity and specificity for the ADOS in differentiating children with autism and ASD from children with non-spectrum disorders (Lord et al., 2001, 2008).
Various studies have examined the effectiveness of ADOS as it is used in clinical practice. For example, Mazefsky and Oswald (2006) examined the diagnostic utility and discriminative ability of the ADOS using a clinical population of 75 children referred to a specialty diagnostic clinic over a 3 year time span. They reported 77% agreement between ADOS classification and team diagnosis, with most discrepancies being in autism versus ASD. The authors note that their results (lower sensitivity) likely reflect the participation of children who present for assessments in common clinical practice. In contrast, the symptom presentation of the children used in the original studies to develop the psychometric properties of the ADOS included “prototypical” representations of the disorders and excluded those with questionable diagnoses. This suggests that clinical expertise and experience with children with ASD is an essential supplement to the ADOS and other assessment instruments for the less “‘clear-cut” cases often seen in typical practice.
A current study also investigated the diagnostic validity of the ADOS in a clinical sample (Molloy, Murray, Akers, Mitchell, & Manning-Courtney, 2011). ADOS classifications were compared to final diagnoses given to 584 children referred for evaluation for a possible ASD in a children’s medical center. Sensitivities were moderate to high on the algorithms, while specificities were substantially lower than reported in the original ADOS validity sample. The authors concluded that the higher number of false positives was likely attributable to the composition of their clinical sample which included many children with a broad range of developmental and behavioral disorders. The results of this study also suggest that clinical populations for which the ADOS is regularly used may be substantially different from the research samples on which it was normed. As a result, it is especially important that the ADOS not be used as a “stand-alone” assessment so as to minimize misclassification in clinical settings where there are children with many other developmental or behavioral disorders.
The role of the ADOS in the assessment of ASD in school and community settings has received attention as well. The perceived advantages and disadvantages of the ADOS were examined via a national survey of practicing school and clinical psychologists (Akshoomoff, Corsello, & Schmidt, 2006). Perceived advantages of the ADOS included its strength in capturing ASD-specific behaviors and the standardized structure provided for observation, while diagnostic discrimination and required resources were the most commonly identified disadvantages. Respondents listing advantages of the ADOS indicated that it captured ASD behaviors, both generally and specifically, and that it was a good measure for identifying behaviors that are difficult to observe or probe in other situations. Respondents indicated that a disadvantage of the ADOS is that it tends to over classify other diagnostic groups as ASD and does not discriminate well within ASD subgroups. Of those that indicated resources as a disadvantage, nearly all indicated time of administration as a disadvantage.
The Autism Diagnostic Observation Schedule (ADOS) is one of the few standardized diagnostic measures that involves scoring direct observations of the child’s interactions and accounts for the developmental level and age of the child. It has the most empirical support among observation-based diagnostic assessment procedures for autism and is recommended in several best practice guidelines as an appropriate standardized diagnostic observation tool (National Research Council, 2001; Wilkinson, 2010). The ADOS offers the practitioner a standardized observation of current social-communicative behavior with excellent interrater reliability, internal consistency and test–retest reliability on the item, domain and classification levels for autism and non-spectrum disorders. Psychometric properties reflect consistent differentiation of autism and ASD from non-spectrum individuals, with less reliable differentiation of autism from ASD (Lord et al., 2001, 2008).
Practitioners should consider the following points when using of the ADOS in clinical and school settings.
1. It is important to distinguish between an ADOS classification and an overall diagnosis of autism. The ADOS is intended to be but “one source” of information used in making a diagnosis of ASD. Because coding is made from a single observation, it does not include information about onset or early developmental history. ADOS algorithms include items coding social behaviors and communication but do not offer an adequate opportunity to measure restricted and repetitive behaviors (though such behaviors are coded if they occur). This means that the ADOS alone cannot be used to make complete standard diagnoses. 
2. The goal of the ADOS is to provide standardized contexts in which to observe the social-communicative behaviors of individuals across the life-span in order to assist in the diagnosis of autism and other ASD. It provides information only on current behavior and was not developed to measure changes over time. Therefore, the ADOS domain or total scores are not a good measure of response to treatment or of developmental gains, especially in the later modules (Lord et al., 2008).
3. The usefulness of the ADOS is related to the examiner’s clinical skills and experience with the instrument. Training and practice in administering the activities, scoring, and observation is required. The ADOS should be administered by an experienced clinician with appropriate training who can use both quantitative and qualitative information to form a clinical impression from the standard activities.
4. Studies suggest that clinical populations for which the ADOS is used may be substantially different from the research samples on which it was normed. As the authors caution, the instrument is not meant to be used as a “stand-alone” assessment. Supporting information from a developmental history, additional observational information or a detailed parent interview are needed for a comprehensive diagnosis. This is especially important in any clinical and school settings where children with various other developmental or behavioral disorders are referred and evaluated.
5. Agreement between clinical diagnostic decisions and standardized diagnostic measures is difficult for children with less typical presentations than classic autism. As a result, diagnostic measures are likely to have difficulty with specificity and sensitivity for children with ASD who do not present with classic features of autism. Further research on the ADOS is needed with children who have an ASD other than autism and with a broader range of children typically seen in clinical and school settings.
Akshoomoff, N, Corsello, C., & Schmidt, H. (2006). The role of the Autism Diagnostic Observation Schedule in the assessment of autism spectrum disorders in school and community settings. The California School Psychologist, 11, 7-19.
Lord, C., Risi, S., Lambrecht, L., Cook, E. H., Leventhal, B. L., DiLavore, P C, et al. (2000). The Autism Diagnostic Observation Schedule-Generic: A standard measure of social and communication deficits associated with the spectrum of autism. Journal of Autism and Developmental Disorders, 30, 205-223.
Lord, C., Rutter, M., DiLavore, P. C., & Risi, S. (2008). Autism Diagnostic Observation Schedule Manual. Los Angeles: Western Psychological Services.
Mazefsky, C.A., & Oswald, D.P. (2006). The discriminative ability and diagnostic utility of the ADOS-G, ADI-R, and GARS for children in a clinical Setting. Autism, 10, 533–49.
Molloy, C. A., Murray, D. S., Akers, R., Mitchell, T., & Manning-Courtney, P. (2011). Use of the Autism Diagnostic Observation Schedule (ADOS) in a clinical setting. Autism, 15, 143-162.
National Research Council. (2001). Educating children with autism. Washington, DC: National Academy Press.
Wilkinson, L. A. (2010). A best practice guide to assessment and intervention for autism and Asperger syndrome in schools. London: Jessica Kingsley Publishers.

Lee A. Wilkinson, PhD, CCBT, NCSP is author of the award-winning book, A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools, published by Jessica Kingsley PublishersHe is also editor of a text in the APA School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools, and author of Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT. His latest book is A Best Practice Guide to Assessment and Intervention for Autism Spectrum Disorder in Schools, (2nd Edition).

© Lee A. Wilkinson, PhD

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