A diagnosis of autism spectrum disorder (ASD) is based on behavioural observation and developmental history and involves a multidisciplinary team of health professionals. There are now calls for the introduction of a more standardised approach to assessment and diagnosis, writes Karen Keast.


There is no one simple test to assess and diagnose autism spectrum disorder (ASD).

Best practice for a diagnosis of autism spectrum disorder involves a multidisciplinary team of health professionals, including a paediatrician or a child psychiatrist along with a psychologist, speech pathologist or an occupational therapist.

Diagnosis of autism spectrum disorder

Dr Josephine Barbaro, a research fellow at the Olga Tennison Autism Research Centre (OTARC) at La Trobe University, says a diagnosis can only occur through behavioural observation and through developmental history.

“That involves interviewing parents and observing the child; we don’t have any concrete biological markers that we can pare up with our observations at this stage,” she says.

When making a diagnosis of autism spectrum disorder, health professionals will use the latest version of the standard criteria for the classification of mental disorders, the Diagnostic and Statistical Manual of Mental Disorders - the DSM-5, produced by the American Psychiatric Association in 2013.

The new edition, which replaces the fourth edition of the DSM, introduced major changes to the diagnostic definitions of autism and its related conditions.

The fifth edition features a single diagnosis of autism spectrum disorder with a severity ranking of levels one, two or three, depending on the amount of support the child requires.

Under the DSM-5, a diagnosis of autism spectrum disorder replaces the previous range of conditions such as Autistic Disorder, Asperger’s Disorder and Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS).

Health professionals now diagnose autism spectrum disorder on the basis of difficulties in two areas.

The first area is social communication deficits, where the child rarely or never uses language, doesn’t respond to people or doesn’t copy people’s actions.

The other area is fixated interests and repetitive behaviours, where the child has an intense interest in certain objects and plays with them in a particular way, such as lining objects up.

This area includes sensory sensitivities, where a child will overreact or under-react to stimuli such as the sound of a ticking clock or the noise of a hand-dryer in public toilets.

The DSM-5 includes a new diagnostic label of Social Communication Disorder (SCD).

SCD is similar to ASD but is diagnosed based on difficulties with both verbal and non-verbal social communication skills and does not include the ASD definition of fixated interests and repetitive behaviours.

Under the change, some children who would previously have received a diagnosis of ASD may now receive this new diagnosis of SCD.

Importantly, those diagnosed under the previous DSM retain their diagnosis and are not required to be re-assessed.

When it comes to diagnosing autism, there are a range of diagnostic assessment tools clinicians use, including two considered to be gold standard - the Autism Diagnostic Observation Schedule (ADOS-2) and the Autism Diagnostic Interview (ADI-R).

Dr Anne Chalfant, a clinical psychologist who specialises in autism and is director of Annie’s Centre, says the ADI-R is a structured interview conducted with parents or the primary caregiver of the child.

“For a hypothetical example, John is three and when he and his parents come in for assessment about John, the clinic should sit down with the parents and go through this standardised interview process, asking the parents questions all about John’s developmental history to date and his milestones,” she explains.

“They’re very detailed questions looking for what we call behavioural evidence - so concrete behaviours that we can code using the assessment tool to do with his social and communication skills and repetitive behaviours.

“All of the questions are basically designed to bring to life, if you like, the diagnostic criteria for autism spectrum disorder in a way that clinicians can then analyse and in a standardised way, in a way that’s reliable between one clinician and the next, and makes sense of the information that the parent gives them.”

The ADOS-2 is a standardised diagnostic measure used to observe the child which targets the symptoms of autism spectrum disorder.

Dr Chalfant says the tool focuses on mostly play-based activities.

“Those activities are designed to draw out the features of an autism spectrum disorder if they’re present for that child,” she says.

“Another hypothetical example is if you have a two-year-old coming for an assessment at the clinic and they had very little language and there was high suspicion of autism, the tool might involve things like the way they play with certain toys, certain play routines, things like peekaboo, pretend birthday parties, games to do with bubble or balloon play, etc.

“What you’re looking for, in a standardised way, is a certain type of response from the child - so you’re looking for things like repetitive behaviours, lack of eye contact, all of the things that are part of the diagnostic criteria for autism.

“We have these activities in order to draw them out and again code them in a way that is standardised and normed against other children their age, against other children with other types of difficulties, so that we can make solid conclusions as to whether it seems like there is quite a high likelihood that the child has a diagnosis or not.”

Clinicians require training to use the gold standard diagnostic assessment tools.

Training is available through Annie’s Centre in Sydney, La Trobe University and Monash University in Melbourne, and through a Graduate Certificate in Autism Diagnosis at the University of Western Australia.

Push for a standardised approach

The Cooperative Research Centre for Living with Autism (Autism CRC), which works in partnership with OTARC, is examining diagnostic practices for autism spectrum disorder across Australia and aims to establish a baseline of current assessment processes.

The study is an essential first step towards developing national standards for autism spectrum disorder diagnosis in Australia.

Dr Chalfant says for too long, assessment of autism spectrum disorder has varied from clinician to clinician depending on their interpretation of social and communication deficits as well as fixated and repetitive behaviours.

That variation can lead to different professional opinions on a child’s diagnosis which can steer the family in the wrong direction for intervention.

“We need a standardised assessment process because we want to be making sure that we are getting it right when we are diagnosing these kids, that we are picking up on the right kind of children and that we are not missing anybody but equally that we are not over-assessing or over-diagnosing,” she says.

Dr Chalfant says a gold standard assessment should involve a medical review, the use of the ADOS-2 and ADI-R tools, plus observation of the child in their natural setting, either at home, kindergarten or school.

She says clarity around assessment will ensure children access the right type of early intervention.

“We want to make sure these children can access the funding support they so desperately need to fund intervention, because intervention hours are huge and they cost a lot of money,” she says.

“Equally, from the taxpayer and the government’s perspective in terms of limited funds and scarce resources, we want to ensure we are not over-diagnosing children and stretching the funding dollar too thinly across children who don’t warrant that diagnosis and could perhaps be assisted through other types of intervention that may not attract funding.”

Rewards of diagnosis and intervention

Dr Chalfant says it’s incredibly rewarding working with children with autism spectrum disorder and their families.

“These children are quite incredible - their interests, even when they’re strong, fixated interests can be fascinating,” she says.

“You see children with a great spread of abilities, so children who essentially in terms of their functioning are non-verbal and very low functioning but who can read, so the mix of presentations that you see can be quite challenging but so interesting.”

Crucially, an accurate diagnosis provides families with valuable information about their child’s needs and points them in the right direction with intervention, Dr Chalfant adds.

“It’s rewarding knowing you can assist and make a difference in that family’s life and in that child’s life rather than them going around in circles, chasing their tails, and not understanding what their child’s needs are.”


Did you know? OTARC has launched a free smartphone app, ASDetect, that enables parents, caregivers and health professionals to identify autism earlier. The app does not provide a diagnosis of autism spectrum disorder, instead it’s designed to provide parents with an indication as to whether they should seek professional opinion.