The Autism Diagnostic Observation Schedule (ADOS) is a standardized assessment used by trained professionals to help in the evaluation of autism spectrum disorder (ASD). The assessment uses semi-structured activities and social situations for a clinician to observe an individual’s communication skills, social interactions, and imaginative use of materials. The primary goal is to create a setting where specific behaviors can be observed in a consistent manner.
This evaluation is a dynamic observation that lasts between 40 and 60 minutes, not a traditional test. The clinician presents planned social events designed to elicit behaviors relevant to an ASD diagnosis. By engaging the person in these activities, the professional gathers information about their social responses, communication patterns, and play skills in a controlled environment.
The Different ADOS Modules
The ADOS is not a one-size-fits-all assessment; it is composed of five distinct modules. A clinician selects the appropriate module based on the person’s chronological age and expressive language ability. This customization ensures that the activities are suitable for the individual’s developmental level, providing a more accurate picture of their skills.
The modules are structured to cover the entire lifespan, from toddlers to adults.
- The Toddler Module is for children between 12 and 30 months who do not consistently use phrase speech.
- Module 1 is for children 31 months and older who also do not use phrase speech.
- Module 2 is intended for individuals of any age who use some phrase speech but are not yet verbally fluent.
- Module 3 is designed for verbally fluent children and young adolescents and includes more complex conversational tasks.
- Module 4 is for verbally fluent older adolescents and adults, featuring activities and questions tailored to their life experiences.
This tiered approach allows the ADOS to be a relevant tool across a wide spectrum of ages and abilities.
How ADOS Scores Are Determined
During the ADOS administration, a clinician observes and rates specific behaviors based on a predetermined coding system. Each behavior is assigned a score, often on a scale from 0 to 3. A score of 0 indicates the behavior is not present or falls within a typical range, while higher scores suggest evidence of behaviors associated with autism. These observations are guided by detailed criteria in the test manual.
The clinician records codes for behaviors across domains like social communication and restricted or repetitive behaviors. After the observation, the individual codes are converted into algorithm scores. This process involves summing the scores for specific items identified through research as being most indicative of ASD to create a total score.
The ADOS-2 introduced a Comparison Score, also called a Calibrated Severity Score (CSS), to standardize results across modules and age groups. This score translates the raw total into a 1-to-10 scale, which provides a measure of the severity of observed symptoms. This allows for a more consistent interpretation of symptom levels, regardless of which module was used or the individual’s age.
Interpreting the Score Ranges
The numerical scores from the ADOS correspond to classifications that indicate the level of evidence for ASD observed during the assessment. For Modules 1 through 4, the total algorithm score falls into one of three ranges: “non-spectrum,” “autism spectrum,” or “autism.” A score below the first cutoff is considered non-spectrum, meaning there was minimal evidence of ASD-related behaviors.
A score that falls between the first and second cutoff places the individual in the “autism spectrum” range, suggesting behaviors consistent with ASD. A score that exceeds the higher cutoff falls into the “autism” classification, indicating the observed behaviors are more significantly aligned with an ASD profile. These cutoff points vary slightly between modules to account for developmental differences.
The Calibrated Severity Score (CSS) provides another layer of interpretation on a 10-point scale. A CSS score from 1 to 3 reflects minimal to no evidence of ASD-related symptoms. Scores from 4 to 5 suggest a low to moderate level of concern, while scores from 6 to 10 indicate a moderate to severe level. For the Toddler Module, scores are given as “ranges of concern” rather than formal classifications to avoid premature labeling at a young age.
The Score’s Role in a Comprehensive Evaluation
An ADOS score, regardless of the number, is not a diagnosis on its own. The ADOS is one component of a comprehensive diagnostic evaluation, and a qualified clinician makes a final diagnosis only after integrating information from multiple sources. The score provides data about observed behavior in a specific setting but does not capture the full picture of an individual’s life.
A thorough evaluation includes a detailed developmental history gathered from parents or caregivers, often using an interview like the Autism Diagnostic Interview-Revised (ADI-R). The clinician also conducts observations of the individual in different contexts. They may also seek input from teachers or family members to understand how the person functions in everyday environments.
This multi-faceted approach ensures a diagnosis is based on a convergence of evidence, not the outcome of a single test. The ADOS provides a structured piece of the puzzle, but the clinician must synthesize all available information. The final diagnostic conclusion reflects a holistic understanding of the individual’s strengths and difficulties.