Currently, there is no one single medical test that will definitively diagnose audlts with autism. Instead, the diagnosis is made on the basis of observable characteristics of the individual.

Here is an overview of some of the different diagnostic standards:

I. Autism Diagnostic Interview-Revised (ADI-R)

The Autism Diagnostic Interview-Revised (ADI-R) is a clinical diagnostic instrument for assessing autism in children and adults. The ADI-R is a semi-structured instrument for diagnosing autism in children and adults with mental ages of 18 months and above. The instrument has been shown to be reliable and to successfully differentiate young children with autism from those with mental retardation and language impairments. The ADI-R focuses on behavior in three main areas and contains 111 items which specifically focuses on behaviors in three content areas - they are:

Quality of social interaction, (e.g., emotional sharing, offering and seeking comfort, social smiling and responding to others);

Communication and language (e.g., stereotyped utterances, pronoun reversal, social usage of language); and