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Diagnosis is an important part of the clinical pathway for autistic individuals. A diagnosis can provide important information to facilitate self-understanding or understanding of another person, as well as information that can help determine the most appropriate supports for people to meet their goals. However, diagnosis of autism is not a straightforward clinical task, and requires specific knowledge, skills, and experience. Having an evidence-based Guideline that provides a consistent, high-quality clinical framework is critical to ensuring that practitioners can work effectively, safely and appropriately in conducting assessments for autism in Australia.

In 2018, Autism CRC published Australia’s first National Guideline for the Assessment and Diagnosis of Autism Spectrum Disorders in Australia. The Guideline combined systematic reviews of the research literature with extensive community consultation within the Australian community. The Guideline was approved by the National Health and Medical Research Council (NHMRC), denoting that it was developed to the highest international standards. The Guideline is now widely adopted throughout Australia, additionally, it is underpinned by a variety of professional resources, for practitioners and the community. The success of the Guideline in improving the quality and consistency of practice in Australia is due to the individual efforts of practitioners, as well as endorsement and support from peak professional and community bodies that have provided expert insight and support for implementation activities. NHMRC approval requires that Guidelines are updated every five years.

Update of the Guideline

This is the first update of this Guideline. In the past five years, there has been a significant change within the community in how autism is understood. For example, autism is no longer considered a disorder to be ‘cured’ but rather intrinsic to the individual, and for some people, their identity. The Guideline now uses identity-first language based on the preferences of the autistic and autism communities, while acknowledging that each person’s individual preferences should be respected in clinical practice. In addition, evidence to inform clinical practice has also increased, such as in relation to telehealth delivery. Understanding and incorporating such changes helps to ensure the Guideline is up to date, evidence-based, relevant, and helpful to all those who use it and who are affected by its use.

There are, however, some challenges with assessment and diagnosis that are largely unchanged. To illustrate, in completing the update, the Guideline Development Group received feedback from the autistic and autism communities that access to timely and affordable assessment and diagnosis services remains out of reach of many people. Evidence from this consultation, and research more broadly, consistently demonstrates that it is marginalised people who have the greatest access barriers, which includes Aboriginal and Torres Strait Islander Peoples, as well as people who are culturally and linguistically diverse, are socially disadvantaged, have complex health and communication needs, and/or live in rural and remote areas. This Guideline cannot address these systemic challenges to equitable service access, but it does specify what services should look like and how they should be delivered.

As with any Guideline update, the key question many will ask is ‘what has changed?’ The structure and format have changed, to (a) reflect implementation of the international standard for Guideline development (GRADE), (b) provide readers with a more concise set of Recommendations, and (c) adopt a similar structure across Autism CRC Guidelines to make them easier to read and follow. The overall number of Recommendations has reduced, even though new Recommendations (e.g., neurodiversity-affirming practice) have been added. This has been possible through revising the Guideline questions and reducing repetition. Finally, some terminology has changed. For example, rather than refer to a ‘Single Clinician Diagnostic Evaluation,’ the Guideline refers to a ‘Lead Practitioner Diagnostic Evaluation’ to emphasise the practitioner leads the process but draws on information and evidence from all relevant sources including involvement of other practitioners.

The Guideline’s purpose, scope, intended audience, and rigorous process through which it has been developed remain unchanged. In 2018, this was the first NHMRC-approved National Guideline relating to autism in Australia, and it presented Recommendations reflecting multiple converging sources of evidence from research, clinical practice, and the views and preferences of the autistic and autism communities. The 2023 Guideline update combines new evidence and perspectives with those from the original, resulting in revised Recommendations where required.

Purpose and objectives

This Guideline was developed to support practitioners involved in clinical assessment that may result in a diagnosis of Autism Spectrum Disorder (ASD) according to the Diagnostic and Statistical Manual of Mental Disorders which is currently in its 5th edition (DSM-5-TR; American Psychiatric Association, 2022) and the World Health Organization’s International Statistical Classification of Diseases and Related Health Problems, which is currently in its 11th edition (ICD-11; World Health Organization, 2019). The specific objectives were to develop a Guideline that:

  • Describes a rigorous framework for accurately determining whether an individual meets the criteria for a clinical diagnosis of autism.
  • Outlines a comprehensive approach to identify related support needs.
  • Contains sufficient flexibility to apply to the assessment of a child, adolescent or adult of any age, gender, cultural or language background, communication or intellectual capacity, and medical complexity, living anywhere in Australia.
  • Describes a feasible process for clinical service providers to administer across the full breadth of community settings in Australia, including public and private healthcare settings.
  • Meets the needs and expectations of individuals being assessed and their caregivers.


The Guideline is focused on assessment that is conducted where a clinical diagnosis of autism is being considered. The process includes making a referral, Assessment of Functioning, Medical Evaluation, and Diagnostic Evaluation. The scope of the Guideline update – which is unchanged from the original Guideline – was determined prior to the commencement of the research and community consultation activities, and is summarised in Table 1.

Table 1. The scope of the Guideline.


In scope

Out of scope

Recipients of services

Children, young people, and adults of all ages, for whom a clinical diagnosis of autism may be relevant.

Children, young people, and adults not meeting this criterion.

Focus of assessment

Assessment where a diagnosis of autism is being considered. This includes assessment of individual characteristics, strengths, and supports needs, whether or not the assessment leads to a Diagnostic Evaluation and decision.

Assessment where a diagnosis of autism is not being considered, or that focuses solely on goal setting and/or support planning.

Outcomes of assessment

Sharing and documentation of findings, as well as recommendations for supports where relevant.

The provision of supports following assessment and diagnosis, irrespective of whether a diagnosis of autism was given.

In presenting the scope, two considerations are highlighted:

  • People access medical and allied health assessments for a variety of reasons. For example, a person may seek an assessment if they have a difference or delay in development, are experiencing restrictions and/or barriers in life activities, and/or may have a diagnosable condition. A person may also access an assessment to better understand their experience of the world, but not be seeking a clinical diagnosis. In each case, the practitioner would work within their scope of practice to meet the client’s needs. The Guideline focuses specifically on clinical diagnosis of autism, rather than attempt to account for all possible reasons for assessment or to provide recommendations for all aspects of practice.
  • It is critical that an assessment for autism takes place in the context of a broader neurodevelopmental and behavioural assessment. This Guideline is intended to operate within the assessment processes applicable to working with children, adolescents, and adults presenting with characteristics of a broad range of neurodevelopmental conditions.

Target users

The primary target users of this Guideline are Australian practitioners who conduct assessments that may result in a clinical diagnosis of autism.

Secondary target users of this Guideline include the following groups:

  • Individuals who have characteristics that may be explained by an autism diagnosis, as well as others (e.g., partners, family) who can use this Guideline to understand how to initiate, and what to expect from, assessment for autism.
  • Australian medical, nursing, allied health, and education professionals and organisations who work with children, young people, and/or adults who show characteristics of autism can use this Guideline to know when and how to make a referral for autism assessment.
  • Australian medical, nursing, allied health, and education professionals and organisations who work with autistic people can use this Guideline to understand what assessments should involve, to ensure Recommendations are implemented and avoid duplication of services.
  • Australian training providers, including peak bodies and tertiary institutions, can use this Guideline to tailor educational and clinical resources, courses, and qualifications to ensure participants achieve the learning outcomes required to contribute to assessment for autism, where doing so will be within their scope of practice and consistent with Guideline Recommendations.
  • Australian funding bodies can use this Guideline to align resource allocation with the recommended process for assessment and diagnosis of autism.

Diagnostic criteria for autism

There are two sets of diagnostic criteria commonly used throughout Australia and the world. The American Psychiatric Association publishes the Diagnostic and Statistical Manual of Mental Disorders which is currently in its 5th edition (DSM-5-TR; American Psychiatric Association, 2022). The World Health Organization publishes the International Classification of Diseases, which is currently in its 11th edition (ICD-11; World Health Organization, 2019).