The Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) is a specialized, activity-based assessment tool used by trained clinicians to help diagnose Autism Spectrum Disorder (ASD) in individuals from 12 months of age through adulthood. This standardized procedure creates a structured environment to observe behaviors relevant to an ASD diagnosis, such as communication and social interaction skills. The ADOS-2 is considered a leading method for behavioral observation, offering a uniform way to evaluate symptoms across different people and settings. It provides a systematic observation of the individual’s social-communicative profile, helping professionals understand the nature and severity of observed symptoms.
The Role of ADOS in Diagnosis
The ADOS-2 provides a structured method for observing specific behaviors associated with ASD in a controlled setting. It is designed to elicit and capture real-time behaviors related to social communication, reciprocal social interaction, and restricted or repetitive behaviors. Unlike less structured clinical interviews, the ADOS-2 uses a predetermined set of activities and “presses” to create situations where these targeted behaviors are likely to occur naturally.
The assessment is highly standardized, ensuring that the materials, procedures, and observation criteria are consistent regardless of the clinician or location. This standardization is important for reliability and validity. However, the ADOS-2 is not a standalone test; it must always be interpreted alongside other information.
A complete diagnostic evaluation requires combining the ADOS-2 results with the individual’s developmental history, caregiver information, and clinical judgment. Tools like the Autism Diagnostic Interview-Revised (ADI-R) often complement the ADOS-2 by gathering detailed historical information. The ADOS-2 score aids in confirming diagnostic criteria but is not the sole determinant for an ASD diagnosis.
Administering the ADOS Assessment
The administration of the ADOS-2 begins with the clinician selecting the appropriate module from the five available options. The module is chosen based on the individual’s expressive language level and chronological age to ensure the activities are developmentally suitable. For instance, the Toddler Module is used for children between 12 and 30 months who have minimal speech, while Modules 3 and 4 are designed for verbally fluent children, adolescents, and adults.
The assessment typically takes between 40 to 60 minutes and is administered by a specialized clinician. The setting is usually a comfortable, quiet room that allows for focused, one-on-one interaction. The clinician presents a series of standardized activities and tasks designed to prompt spontaneous social and communication behaviors.
These activities vary significantly across modules to match the person’s age and language skills. For younger children, this might involve construction tasks, joint play scenarios, or imitation games to observe shared enjoyment and nonverbal communication. For older, verbally fluent individuals, the tasks shift to conversation prompts, describing a picture, or discussing emotions and social difficulties. The goal of every activity is to provide a standardized opportunity for the individual to display behaviors relevant to the diagnostic criteria.
Interpreting the Test Results
After the assessment is complete, the clinician systematically scores the observed behaviors across domains such as communication, social interaction, and restricted behaviors. Specific behaviors are assigned numerical values, typically on a scale from 0 to 3, where higher numbers indicate a greater presence or severity of the autism-related trait. These raw scores are then converted using algorithms tailored to the individual module.
A significant component of the scoring is the calculation of the Calibrated Severity Score (CSS), which ranges from 1 to 10. The CSS is a standardized metric that allows clinicians to quantify the severity of ASD symptoms and compare them across individuals who took different modules. A higher CSS score indicates a greater level of autism-related symptomatology, with a score of 4 or higher suggesting a classification on the autism spectrum.
The resulting ADOS-2 score provides an objective measure of observed behaviors, but it does not equate to a definitive medical diagnosis. The final diagnostic decision rests with a qualified professional, such as a developmental pediatrician or psychologist. They integrate the ADOS-2 scores, the CSS, the developmental history, and other clinical observations to determine if the individual meets the full diagnostic criteria for Autism Spectrum Disorder.