Autism Diagnostic Observation Schedule

The Autism Diagnostic Observation Schedule was created by Catherine Lord, Michael Rutter, Pamela C. DiLavore and Susan Risi in 1989.[1] It became commercially available in 2001 through Western Psychological Services.[2]

The ADOS consists of a series of structured and semi-structured tasks, and generally takes from 30 to 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.[2]

Each subject is administered activities from just one of five modules (T, 1, 2, 3, 4). The selection of an appropriate module is based on the developmental and language level of the patient. The only developmental level not served by the ADOS is that for adolescents and adults who are nonverbal.[1] 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.

Module 1 is used with children who use little or no phrase speech. Subjects who do use phrase speech, but do not speak fluently, are administered Module 2. Since these modules both require the subject to move around the room, the ability to walk is generally taken as a minimum developmental requirement for use of the instrument as a whole. Module 3 is for children/adolescents who are verbally fluent, and Module 4 is used with older adolescents and adults who are verbally fluent. Some examples of Modules 1 or 2 include response to name, social smile, and free or bubble play. Modules 3 or 4 can include reciprocal play and communication, exhibition of empathy, or comments on others' emotions.[1] A major difference between Modules 3 and 4 is the reliance of Module 4 primarily on questions and verbal responses (as opposed to actions during play).

A revision, the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2), was released in May 2012. It includes 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.[3]

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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 level of false positives has been observed in adults with psychosis;[6] 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.[7] 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).[8][9] 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.[10]

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.[11]