Autism Diagnostic Observation Schedule (ADOS)

The ADOS-2 has five modules selected by age and language level. Module T (toddlers, 12–30 months), Module 1 (no consistent phrase speech), Module 2 (phrase speech), Module 3 (verbally fluent children and young adolescents), Module 4 (verbally fluent older adolescents and adults). The session lasts 45–60 minutes and is video-recorded for scoring.

The administrator is a clinician trained in the ADOS-2, typically a clinical psychologist, paediatrician, child psychiatrist, or specialist SaLT. UK accredited training is delivered through the Centre for Autism / WPS. The scoring algorithm produces a Comparison Score (1–10) where 1–3 indicates minimal to no evidence, 4–5 indicates low evidence, 6–7 indicates moderate evidence, and 8–10 indicates a high level of autism-related behaviour.

The ADOS-2 is observation, not interview. It measures what the child does in a structured interaction at a single point in time. It can be affected by mood, fatigue, anxiety, and the rapport with the assessor. A child who has learned to mask in social settings (commonly older girls) may produce a Comparison Score that under-represents their underlying autism. A child mid-meltdown will produce a score that over-represents it.

The ADOS-2 alone is not a diagnosis. NICE CG128 requires a multi-disciplinary autism assessment: a developmental history (ADI-R or 3Di or equivalent), an observation (typically ADOS-2), and consideration of the wider clinical picture. A confident autism diagnosis can sometimes be made without an ADOS-2 if the clinical picture is unambiguous; conversely, an ADOS-2 result alone cannot diagnose autism without the developmental history.

In an EHC needs assessment context, ADOS-2 results are routinely reported in paediatric letters and EP reports, supporting Section B description of the child's autism profile.