| Autism Diagnostic Observation Schedule | |
|---|---|
| Purpose | assess autism in children, adolescents, and adults |
The Autism Diagnostic Observation Schedule (ADOS) is a standardized diagnostic test for assessing autism spectrum disorder. The protocol consists of a series of structured and semi-structured tasks that involve social interaction between the examiner and the person under assessment. The examiner observes and identifies aspects of the subject's behavior, assigns these to predetermined categories, and combines these categorized observations to produce quantitative scores for analysis. Research-determined cut-offs identify the potential diagnosis of autism spectrum disorder, allowing a standardized assessment of autistic symptoms.
The Autism Diagnostic Interview-Revised (ADI-R), a companion instrument, is a structured interview conducted with the parents of the referred individual to cover the subject's full developmental history. The ADI-R has lower sensitivity but similar specificity to the ADOS.
The original ADOS was created by Catherine Lord, Michael Rutter, Pamela C. DiLavore and Susan Risi in 1989.[1]
Responding to the need for diagnostic tools for autism in younger children, researchers developed the Pre-Linguistic Autism Diagnostic Observation Schedule (PL-ADOS).[2] The content of the activities, as well as the general format, were adapted to rely less on conversation.
In 2000, Lord and her colleagues introduced the ADOS-Generic (ADOS-G) as a means to assess a broader developmental range of individuals. The ADOS-G introduced a module format, allowing for different protocols to be used depending on developmental and language factors.[3] It became commercially available in 2001 through Western Psychological Services.[4]
A second edition was published in 2012 to include updated norms, improved algorithms for Modules 1 to 3, and a new Toddler Module (T) that facilitates assessment in children ages 12 to 30 months.[5][6] Changes were also made to the algorithm to report on domains more in line with the recent changes to diagnostic criteria in the DSM-5. Whereas the ADOS-G determined social, communication, and social-communication domains, the ADOS-2 combined these domains to represent social affect, and added a new domain to assess restrictive and repetitive behaviors (RRB).
The ADOS consists of a series of structured and semi-structured tasks that generally takes 30-60 minutes to administer. During this time, the examiner provides a series of opportunities for the subject to show social and communication behaviors relevant to the diagnosis of autism.[4] Each subject is administered activities from the module that corresponds to their developmental and language level. The ADOS should not be used for formal diagnosis with individuals who are blind, deaf, or otherwise seriously impaired by sensory or motor disorders, such as cerebral palsy or muscular dystrophy.
Following task administration and observation coding, a scoring algorithm classifies the individual with autism, autism spectrum disorder, or non-spectrum disorder. The toddler module algorithm yields a "range of concern" rather than a definite classification.[7]
The toddler module is appropriate for children 12–30 months who use little to no phrase speech. Because social communication and behavioral patterns can be highly variable in the first 2 years of life, the toddler module is typically used to identify areas for continued monitoring rather than to provide a definite diagnosis. The toddler must be able to walk independently.[8] This module consists of eleven primary activities:[7]
Module 1 is appropriate for children 31 months and older who use little or no phrase speech. This module consists of ten activities:[5]
Module 2 is appropriate for children six years old or younger who speak in phrases but have not yet developed fluent verbal language. This module consists of fourteen activities:[5]
Module 3 is appropriate for children or young adolescents who are verbally fluent. This module consists of fourteen activities:[5]
Module 4 is appropriate for older adolescents and adults. While similar to module 3, module 4 relies more heavily on questions and verbal responses rather than non-verbal actions observed during play. This module consists of ten to fifteen activities. Activities marked by an asterisk are optional:
The social communication difficulties that the ADOS and ADOS-2 seek to measure are not unique to ASD; there is a heightened risk of false positives in individuals with other psychological disorders. In particular, an increased false positive rate has been observed in adults with psychosis;[9] while case reports indicate that such false positives may also occur in cases of childhood-onset schizophrenia, which is an exceptionally rare entity with a frequency of 1 in 40000.[10] There is evidence that adults with schizophrenia demonstrate an increased incidence of autistic features compared to the general population, resulting in higher ADOS scores, though schizophrenia patients also experience positive symptoms of psychosis (e.g. hallucinations, delusions, formal thought disorders).[11][12] A 2016 study found that 21% of children with a diagnosis of ADHD (and without a concurrent diagnosis of ASD) scored in the autism spectrum range on the ADOS total score.[13]
A 2018 Cochrane systematic review included 12 studies of ADOS diagnostic accuracy in pre-school children (Modules 1 and 2). The summary sensitivity was 0.94 (95% CI 0.89 to 0.97), with sensitivity in individual studies ranging from 0.76 to 0.98. The summary specificity was 0.80 (95% CI 0.68 to 0.88), with specificity in individual studies ranging from 0.20 to 1.00. The studies were evaluated for bias using the QUADAS-2 framework; of the 12 included studies, 8 were evaluated as having a high risk of bias, while for the remaining four there was insufficient information available for the risk of bias to be properly evaluated. The authors could not identify any studies for the ADOS-2; the scope of the review was limited to preschool age children (mean age under 6 years), which excluded studies of Modules 3 and 4 from the meta-analysis. One included study examined the additive sensitivity and specificity of the ADOS used in combination with the ADI-R; that study found an 11% improvement in specificity (compared to ADOS alone) at the cost of a 14% reduction in sensitivity; however, due to overlapping confidence intervals, that result could not be considered statistically significant.[14]