Diagnosis of Autism Spectrum Disorder (ASD) in Melbourne

Diagnosis of Autism Spectrum Disorder (ASD) requires differential determination as to whether the child or adult is on the autism spectrum, or if the observed behaviours are the result of a medical or other condition. We use a structured method to determine the difference. Often we use prior medical history and assessments and only conduct tests that are necessary for diagnosis. A diagnosis of ASD is made by a team of psychologists and a Clinical Psychologist in accordance with he 2023 best practice guidelines from the Autism Cooperative Research Centre (Autism CRC) in Australia for diagnosing autism in adults emphasize a thorough, multidisciplinary assessment approach. 

DSM-V criteria for ASD

The DSM-5-TR (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision) outlines the criteria for an Autism Spectrum Disorder (ASD) diagnosis as follows:

A: Persistent deficits in social communication and social interaction across multiple contexts. This includes:

Deficits in social-emotional reciprocity (e.g., abnormal social approach, failure of normal back-and-forth conversation)
Deficits in non-verbal communicative behaviours (e.g., poor eye contact, body language, understanding and use of gestures)

Deficits in developing, maintaining, and understanding relationships (e.g., difficulties adjusting behaviour to suit various social contexts, difficulties making friends)

B: Restricted, repetitive patterns of behaviour, interests, or activities, as manifested by at least two of the following:

• Stereotyped or repetitive motor movements, use of objects, or speech
• Insistence on sameness, inflexible adherence to routines, or ritualised patterns of verbal or non-verbal behaviour
• Highly restricted, fixated interests that are abnormal in intensity or focus

• Hyper or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment

C: Symptoms must be present in the early developmental period, but may not become fully manifest until social demands exceed limited capacities, or may be masked by learnt strategies.

D: Symptoms cause clinically significant impairment in social, occupational, or other important areas of current functioning.

E: These disturbances are not better explained by intellectual disability or global developmental delay. ASD and intellectual disability frequently co-occur, but for a comorbid diagnosis, social communication should be below that expected for general developmental level.

We consider all information, including many of the following:

Developmental and clinical history.

• Previous assessments if any
• Parental and school reports
• The Autism Diagnostic Interview (ADI-R) (a parental interview used to examine  early developmental history and current behavioural functioning).
• The Childhood Autism Raring Scale (CARS-2)
• The Autism Diagnostic Observation Schedule (ADOS): This is a structured observational assessment, in which observations are made of the child in a play-like setting.
• The VINELAND 3, a functional questionnaire for parents assessing adaptive behaviours (e.g., learning, dressing, eating etc.).
• The PEDI-CAT Assessment of Capacity to function day to day
• WHODAS WHO disability Assessment Schedule
• Other online assessments are also used for differential screening

The Autism Diagnostic Interview-Revised (ADI-R)

The Autism Diagnostic Interview-Revised (ADI-R) is a structured interview, conducted by a psychologist, with the parents or other adult related to the individual who has been referred for an ASD evaluation. The interview, which has been used by researchers and clinicians for decades, is a diagnostic tool from people aged 18 months and older. It measures behaviour in the areas of reciprocal social interaction, communication and language, and repetitive/restrictive patterns of behaviour.

The ADI-R covers an individual’s entire developmental history and is usually conducted online, by a psychologist. It generally takes around 2 hours. Parents/caregivers are asked 93 questions that examine the following past and current behavioural areas.

• 1) communication
• 2) social development and play
• 3) repetitive and restricted behaviour
• 4) general behavioural issues.

Since the ADI-R is a semi-structured interview, the questions are open-ended in nature. This enables the investigator to obtain all the information required to determine a valid rating for each behaviour. Due to its fluidity, parents and caretakers usually feel comfortable when taking part in this interview. Some people find that participation alone aids their understanding of ASD and the factors that lead to a diagnosis.

Behavioural Observations

Childhood Autism Rating Scale (CARS 2).

Information is obtained about the child's behaviour using standardised rating scales such as the Childhood Autism Rating Scale (CARS 2 ). The CARS 2 is a15-item behaviour rating scale which helps identify children with ASD, distinguishing them from other developmentally handicapped children. The CARS can distinguish mild, moderate,and severe ASD.

The CARS was developed over 15 years and includes items drawn from five prominent systems for diagnosing ASD. Each item covers a particular characteristic, ability, or behaviour. After observing the child and examining the relevant information provided by the child’s parents, a psychologist at BNC rates the child on each item. Using a 7-point scale, the psychologist indicates the degree to which the child’s behaviours deviate from those of a typically developing child of the same age.

Autism Diagnostic Observation Schedule (ADOS-2)

The ADOS-2 is used to evaluate people who have been referred for an ASD assessment from toddlers to adults, whether verbal or non-verbal. Like the ADI-R, the ADOS is a semi-structured assessment. However, unlike the ADI-R, client is present. The child engages, in-clinic, in a variety of activities whilst a psychologist observes their social and communicative behaviours.

The activities provide an relatively normal context in which natural interactions can occur. The ADOS consists of four modules, each 35 to 40 minutes in duration. Depending on their age, the person may complete just one module related to their expressive language level.

Since it offers standardised materials and ratings, the ADOS 2 is a measure of ASD that is unaffected by language level. It can be used across populations and is a cost-effective addition that works with clients with developmental disorders.

Other screening assessments for ASD

Autism Hearing Test 

Before conducting any ASD assessment, a person’s hearing must be assessed. A commonly reported symptom for those with ASD is a lack of response to social overtures and vocalisations (‘acting as though they do nor hear’). Thus, an auditory assessment is essential to exclude the possibility of a hearing impairment which might look like one of the early signs of Autism.

Test for Cognitive Skills

Our ability to learn depends on our cognitive skills. A psychologist at BNC can assess cognitive abilities. A consultation and assessment with an ASD expert can provide valuable information about management strategies and help us formulate an individualised therapy plan for your child.

Receptive and expressive language

Comprehensive tests from a speech pathologist help us determine your child’s expressive and receptive communication skills. Both, verbal (spoken) and non-verbal communication (use of gesture and reading of body language) skills are tested. Many children will also have their pragmatic language skills assessed. Pragmatic language skills refer to how effectively they use their words and gestures to communicate. Assessing language skills includes a comprehension evaluation of their oral motor and speech motor systems, such as:

• Non-speech motor functions: posture, gait, gross and fine movement coordination;oral movement coordination, mouth posture, drooling, swallowing, chewing, oral structures, symmetry, volitional vs. spontaneous movement.
• Speech motor functions: struggle and strain during speech attempts, visible groping of mouth, deviations in prosody (rate, volume, intonation, etc.), fluency of speech, hyper/hyponasality, speech diodochokinesis (involving alternative and sequential speed on consecutive repetitive attempts at utterance), volitional vs. spontaneous attempts.
• Articulation and phonological performance: amount of verbal output, sound repertoire, reluctance to speak, interactive ability, intelligibility and type of errors, effects of performance load and increasing complexity; connected speech sampling.
• Language performance: comprehension and expression, type of utterances, semantic and syntactic ability, effect of increased length of input, conversational abilities.
• Others: ability to sustain and shift attention, reaction to speech, distractibility

 

Updated on:  10/02/2026 By: Dr. Jacques Duff – BA Psych; Grad Dip Psych; PhD; MAPS; MECNS; MAAAPB; MISNR; FANSA
Reviewed on: 20/02/2026 by: Bernard Ferriere - BA; Grad Dip App Psych; Dip Clinical Hypnosis; FCCP; MAPS; MASH; Clinical Psychologist