How do I diagnose Autistic Spectrum Disorders (ASD)?

To make a diagnosis of ASD, a child has to have significant difficulties in the areas of social communication and fixated (or narrow) interests and repetitive behaviours, which are present from early childhood. Different professionals will have different processes for making the diagnosis. The process I like to follow is to try to understand the child's underlying developmental profile (for example, speech or language disorders, motor coordination difficulties, anxiety, inattention, sensory behaviours) by taking a history, reviewing any previous allied health assessments and doing my own independent assessment.  I use modified tasks from a standardised assessment tool called an ADOS (Autistic Diagnostic Observation Schedule) when I do my examination. If a child clearly falls within the autistic range then I am usually happy to make the diagnosis with no further referrals for assessment.  If the child may have a less severe form of ASD then I usually refer the child to an experienced speech therapist for an ADOS, as I find that they can often give the best information about a child's social language and communication skills. The family then come back to me for the formal diagnosis after the ADOS.