A Thorough Presentation of Autism Diagnostic Observation Schedule (ADOS-2)

A Thorough Presentation of Autism Diagnostic Observation Schedule (ADOS-2)

Elpis Papaefstathiou
DOI: 10.4018/978-1-7998-8217-6.ch002
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ADOS-2 is considered the gold standard observational instrument for use in the diagnosis and/or classification of autism and ASD. In this chapter, the process of assessment will be described, which involves direct observation and engagement of children and adults for whom an ASD is suspected. Specifically, an emphasis will be put on ADOS structure, namely the five different modules for the assessment. Then, the advantages of ADOS-2 will be elaborated as a diagnostic tool and a brief review of studies concerning its psychometric properties will be reported.
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As the number of ASD diagnoses is constantly increasing (2010 Principal Investigators & CDC, 2014) and due to the fact that ASD is considered a heterogeneous disorder, the need for diagnostic measurement with high diagnostic accuracy is more than ever imperative. Moreover, it seems that factors such as gender, level of language abilities, cognitive functioning play affect the symptomatology of ASD. For these reasons, the diagnostic process sometimes is extremely challenging.

ADOS was first developed in 1980 and it was mainly used for research diagnoses. It was considered as a reliable tool (Lord et al., 2000). ADOS-2 released in 2012, extending the age range with the addition of the Toddler Module. It is, also, a well-established diagnostic instrument, considered the ¨gold standard¨ for collecting standardized and objective information about social communication and restrictive and repetitive behaviors. It was designed in order to improve the accuracy of the diagnostic algorithms of the previous edition. Many studies have demonstrated the diagnostic accuracy of ADOS-2 as it is highly reliable and valid for the assessment of ASD in children, adolescents and adults.

Structure of ADOS


ADOS-2 includes five assessment modules for the assessment of individuals with different expressive language ability and age (Table 1). Specifically:

The Toddler Module is designed for toddlers who are 12 to 30 months of age and who do not use phrase speech consistently.

Module 1 for children 31 months and older and who do not use phrase speech consistently. For this Module there are two algorithms: Few to No Words, and Some Words.

Module 2 is designed for children of any age who use phrase speech, but they are not verbally fluent. For this Module there are two algorithms: Younger than 5 years, and Aged 5 Years or Older.

Module 3 is for verbally fluent children and young adolescents (approximately 16 years or younger).

Module 4 is designed for verbally fluent older adolescents and adults.

Each module has its own Protocol Booklet that provides order and structure for the administration, coding and scoring (Lord et al., 2012).

There is also a kit. This kit is a large container that includes all the appropriate materials for the five modules that are necessary for the administration such as toys, picture books, snacks, interview questions and others. Many of the materials are used across differed modules and are selected purposely in order to attract the attention of the individual. The duration of the administration ranges between 40 to 60 minutes (Lord et al., 2012).

Activities of Each Module

ADOS-2 includes planned social activities called ¨presses¨ (Murray, 1938). Although the activities across the Modules differ, the general principles remain the same. Their main goal is to provide interesting, standard contexts in which the individual will desire to participate in social interactions. The number of activities differs from module to module. The order of activities and materials can be varied according to the individual needs. In tables 2, 3, 4, 5 and 6 activities of each module are presented separately (Lord et al., 2012).

Key Terms in this Chapter

Specificity: The proportion of negative diagnosis that are correctly identified.

DSM-5: Diagnostic and Statistical Manual of Mental Disorders is the taxonomic and diagnostic tool published by the American Psychiatric Association (APA) for psychiatric diagnoses.

Sensitivity: The proportion of positive diagnosis that are correctly identified.

Social Affect: The one of the two algorithm domains. It includes items pertaining ¨Communication¨ and ¨Reciprocal Social Interaction¨.

Internal Consistency: A measure of reliability that reflects the extent to which items within an instrument measure various aspects of the same characteristic or construct.

Algorithm: A method that uses the test results to identify a health condition.

Predictive Validity: The extent to which the diagnostic tool’s algorithms identify individuals on the autism spectrum.

Reliability: The consistency with which a diagnostic tool estimates what it is designed to measure.

Inter-Rater Reliability: The degree of agreement between raters.

Restrictive Repetitive Behaviors: The one of the two algorithm domains. It includes items pertaining ¨Restrictive Repetitive Behaviors¨.

Test-Retest Reliability: The extent to which a tool yields consistent results when administered in two different occasions.

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