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How is Autistic Spectrum Disorder Diagnosed?

It is important that individuals with Autistic Spectrum Disorder are diagnosed at an early stage, so that appropriate interventions can begin as soon as possible. There is no definitive test used to diagnose Autistic Spectrum Disorder, diagnosis is based on developmental history taking, observations and direct assessment in a range of settings.

Parents/carers may notice the symptoms of an Autistic Spectrum Disorder when the child is around two years old, however mild symptoms may not be detected until adulthood.

For the diagnosis of Autistic Spectrum Disorder, problems in at least one of communication, social skills and/or restricted behaviour will need to be present. Normally the diagnosis will take part in two stages. The first stage will involve developmental screening tests to assess what developmental milestones have been reached and also to identify changes in behaviour. Screening will not provide a diagnosis; it will however help to determine whether additional evaluations by specialist health professionals are required. Several screening instruments have been developed to aid the initial assessment stages, some of which include:

  • The Checklist of Autism in Toddlers - involves questionnaire with the parents/carers and an observation of the child's behaviour
  • The Social Communication Questionnaire - questionnaire