How is Autism Diagnosed in Children?

In this article, we will explore how autism is diagnosed in children in Australia. The first step to get a diagnosis would be to see a paediatrician, child psychologist, or speech pathologist. These practitioners use various assessment tools and skills to evaluate your child’s strengths and weaknesses in different areas of ability. Your GP will need to refer you to a paediatrician if you haven’t seen one yet.

What Aspects Are Assessed?

Direct Observation

The practitioner will be looking for behaviours such as joint attention (if your child engages them in eye contact or communicates with them whilst playing) and whether your child tries to draw the clinician into their play. [1]

Direct observation may include recording the following:

  • Child’s interests
  • What their play looks like and how do they prefer to play
  • Interaction skills & communication methods
  • Eye gaze and attention-sharing (joint attention)

clinician with children


Parental Input

The practitioner will conduct an in-depth conversation assessment with the parents or guardians, to understand your child’s behaviour at home and in other environments. They will inquire about your child’s development and characteristics both when they were younger and how they are today.

  • Detailed conversation with parents about their observations
  • Insight into a child’s early development stages (e.g., smiling, talking as a baby)
  • Daily behaviour and interactions as observed by parents
  • The child’s emotional regulation skills

This information may be combined with information from other sources, such as daycare or school reports to provide a more holistic view.

Different Environments

Assessment may involve a series of scenarios to see how your child reacts to different situations. Observations in clinics, home visits, and other natural settings (e.g., childcare).
The gold standard way of reaching a diagnosis is to take into account the child’s presentation across all areas of their daily life and to include examples of interactions from relevant adults such as parents, teachers, Grandparents, therapists involved in the child’s care.

Developmental Skills

Practitioners may assess the following skills in line with typical developmental timeframes:

  • Fine motor skills (e.g., manipulating objects, completing puzzles)
  • Understanding and use of language (conversational or solely to get their needs met )
  • Comparison of social skills with overall learning development

Child playing with rainbow blocks


How Old Are Children When They Are Diagnosed?

Most children are diagnosed between the ages of 3 and 8. [2]

While some children are diagnosed later, many can be reliably diagnosed as early as 24 months, with 85-95% of these diagnoses remaining accurate in later childhood. [3]

Some factors that can lead to a later diagnosis of autism include the availability of diagnostic services, financial capacity, the type and severity of symptoms, and symptoms that only become noticeable as the person grows older.

How Long Does It Take To Get A Diagnosis?

It takes around 12 months on average to obtain an autism diagnosis in Australia. [3]

However it can vary based on location, wait times for an initial paediatrician appointment and whether more health care practitioners need to be involved in the diagnosis process.

For example, in Sydney, it may take 6-8 months to get an appointment.

If a child already sees a Paediatrician or Psychologist and is well known to them, the process can be expedited.

Can A Paediatrician Make the Diagnosis Or Will We Need a Multidisciplinary Team?

There are two ways a child can receive a diagnosis of Autism Spectrum Disorder. The first is through a paediatrician trained in using psychometric assessments.

The second and more common route is for the paediatrician to refer the child to a psychologist, who will complete the assessment process and write a report using information from assessments, interviews with relevant adults, and observations from various settings.

paediatrician with family


What Does a Mosaic Early Intervention ASD Assessment Involve?

In order to assess whether your child fits or does not fit the diagnostic criteria for a clinical diagnosis of ASD, clinicians will undertake a multi-step assessment process, this will usually take a few weeks from the start of the initial consultation to the receipt of the report.

The Assessment Process

The assessment will involve Psychometric assessments which may or may not involve the child being present, these can sometimes be questionnaire based, or structured interviews with the assessing clinician.

There are a range of different assessments that may be used depending on need, such as the Autism Diagnostic Interview-Revised, Childhood Autism Rating Scale, Social Communication Questionnaire or Vanderbilt Scales for Autism.

The assessing clinician will identify if and what type of assessment would be appropriate to each individual child to ensure all required information is captured.

Collating Information

Data will then be taken from all other Professionals involved in your child’s care (Speech Pathologists, educators, Occupational Therapists, Behaviour Analysts etc) and any other assessments that they may have already had conducted (CELF 5, Vinelands etc).

1:1 Assessment With Your Child

The assessor will then conduct a 1:1 assessment with your child, this usually takes about an hour and it is designed so that the Clinician can observe and gauge your child’s behaviours, communication skills, social interaction abilities and any noted difficulties.

Usually this is achieved using a specific type of assessment called the ADOS-2.
The interviews, questionnaires and assessments will then be marked in order to reach a numerical value which will allow the assessor to combine all this information together to reach a conclusion which could result in a formal diagnosis.

Further detailed information on ASD Assessment:

  • Due to the amount of time each assessment takes, the assessments will normally happen over at least 2 separate sessions
  • Your child does not need to be present for the parents interviews, but does need to attend for the ADOS session and any other observation sessions
  • During the ADOS assessment it is preferred that an adult with whom the child feels comfortable with remains for the session, this can be either a parent, Grandparent or carer
  • Should your child fall outside of the clinical diagnostic borders for a diagnosis of ASD, then the Psychologist will make recommendations for support for the child or suggestions for further assessments
  • On occasions a child may receive an alternative diagnosis
  • At Mosaic we generally use the SDQ (Strengths and Difficulties Questionnaire) which is a questionnaire form completed over email by parents, teachers or educators and (depending on the age of the child) a self-report form
  • We also use the ADI-R (Autism Diagnostic Interview – revised) this is an online telehealth meeting between the Psychologist and parents. This will take between 1.5 and 2 hours to complete.The ADOS 2 is the structured assessment conducted between the child and the Psychologist with a trusted adult present. This takes 1 hour to complete and is conducted in the clinic at Mosaic Early Intervention
  • There are other assessments that we offer if considered necessary such as the Conners Behavioural Rating Scale (CBRS) the Conners 3 (another behavioural rating scale) and the Social Communication Questionnaire (SCQ)


What Are The Benefits To Pursuing An Autism Diagnosis?

Some parents may hesitate to pursue a diagnosis due to uncertainty about their child’s condition, doubts about the benefits of a diagnosis, or financial concerns.

Here are some reasons that getting a diagnosis may be beneficial:

  • Secure funding for essential services and support, including early intervention, speech pathology, occupational therapy, and other necessary resources to aid your child’s development and daily activities
  • Improve classroom support for their learning through tailored teaching methods, additional assistance, or specialised schools
  • Gain a deeper understanding of how your child thinks and processes the world, enabling you and your family to better support them
  • Access communities of families with neurodiverse children to gain additional support, share experiences, and feel a sense of belonging [4]


What Happens After A Confirmed Diagnosis?

Once an autism diagnosis is made, the family is provided a report which contains information on the diagnosis including recommendations for how to support the child for them to achieve their full potential .

The practitioner can make recommendations on clinical and support services as well as how these may be accessed using NDIS funding.

If the family has concerns about the diagnosis, they are welcome to seek another opinion. [5]



How is autism diagnosed in children? Seeking an autism diagnosis for your child begins with consultations with a paediatrician or child psychologist,. Through direct observation, parental input, and various assessments, practitioners can gain a comprehensive understanding of your child’s skills and abilities including things that they may find difficult.

While most children are diagnosed between ages 3 and 8, early diagnosis and intervention are crucial for accessing necessary support and services.

Understanding what’s involved in a diagnosis, as well as the benefits, can empower families to better support their child’s unique needs and development.

We would like to acknowledge Hannah Wise-Mann, Psychologist, for her valuable contribution to this article.



  1. Autism diagnosis for children: a guide
  2. Understanding autism
  3. Parents’ experiences of the service pathway to an autism diagnosis for their child: What predicts an early diagnosis in Australia?
  4. Why pursue a child’s diagnosis
  5. National Guideline For the assessment and diagnosis of autism in Australia

At Mosaic, we understand how difficult it can be to sift through all the information when first receiving a diagnosis or needing support.

For more information please take a look at our FAQ page. If you have any questions or would like to find out more about our service, please get in touch.