This website (previously ASDinfoWales) belongs to and is run by the National Autism Team, which is funded by Welsh Government. It is one of the resources which helps the Team achieve their aim to improve the lives of autistic people in Wales.

I The following advice is adapted from NICE Guideline CG142: Autism in adults: diagnosis and management [Link:]


At the beginning of the assessment, explain the process to the patient, as well as how the results will be fed back to them. Do this in a way that takes into account the individual’s needs and capacity to understand. Where appropriate, you may wish to make use of any accompanying family members, carers etc in explaining the process and supporting them through it.

Obtaining Historical Information

Where possible and appropriate, invite a family member, parent, carer or other informant as well as the patient.

Where possible obtain documentary evidence (e.g. old school reports) of current and past behaviour and early development.

Focus of Diagnostic Assessment

Enquire about and assess the following:

  • core autism signs and symptoms (difficulties in social interaction and communication and the presence of stereotypic behaviour, resistance to change or restricted interests) that have been present in childhood and continuing into adulthood
  • early developmental history, where possible
  • behavioural problems
  • functioning at home, in education or in employment
  • past and current physical and mental disorders
  • other neurodevelopmental conditions
  •  hyper- and/or hypo-sensory sensitivities and attention to detail.

During a comprehensive assessment, take into account and assess for possible differential diagnoses and coexisting disorders or conditions

Where possible, directly observe for core autism signs and symptoms, especially in social situations.

Do not routinely use biological tests, genetic tests or neuroimaging for diagnosis of ASD.

If any of the above risks are identified, develop a risk management plan.

Diagnostic Tools

A diagnostic tool is not necessarily required, but can be useful, particularly for complex assessments.

Diagnostic tools for adults who do not have a learning disability:

the Adult Asperger Assessment (AAA; includes the Autism-Spectrum Quotient [AQ] and the Empathy Quotient [EQ]) (Free)

the Autism Diagnostic Interview – Revised (ADI-R) (£)

the Autism Diagnostic Observation Schedule – Generic (ADOS-G) (£)

the Asperger Syndrome (and high-functioning autism) Diagnostic Interview (ASDI) (Free)

the Ritvo Autism Asperger Diagnostic Scale – Revised (RAADS-R) (Free)

Diagnostic tools for adults who have a learning disability:

  • ADOS-G
  • ADI-R

To organise and structure the process of a more complex assessment, consider using a formal assessment tool, such as the Diagnostic Interview for Social and Communication Disorders (DISCO), the ADOS-G or the ADI-R.

Diagnostic Complexities and Disagreements

Consider obtaining a second opinion (including referral to another specialist autism team if necessary), if there is uncertainty about the diagnosis or if any of the following apply after diagnostic assessment:

  • disagreement about the diagnosis within the autism team
  • disagreement with the person, their family, partner, carer(s) or advocate about the diagnosis
  • a lack of local expertise in the skills and competencies needed to reach diagnosis in adults with autism
  • the person has a complex coexisting condition, such as a severe learning disability, a severe behavioural, visual, hearing or motor problem, or a severe mental disorder


AUTISM: Do you know the SIGNS?
Autism SIGNS Poster - Pre School Children (2 years to 4 ½ years)
Autism SIGNS poster - Children and younger adolescents
Autism SIGNS poster - Older Adolescents and Adults
ASD Assessment planning tool
ICD-10 Diagnostic categories
DSM5 Diagnostic Criteria
RC Psych_Diagnostic Interview Guide for the Assessment of Adults with ASD