Diagnostic manuals, ICD-10 and DSM-5, set out the criteria for autism to be diagnosed. These create the foundation for diagnostic tools such as the DISCO (Diagnostic Interview for Social and Communication Disorders), the ADI-R (Autism Diagnostic Interview - Revised), the ADOS (Autism Diagnostic Observation Schedule) and 3Di (Developmental, Dimensional and Diagnostic Interview). 

These, and other diagnostic tools, are used to collect information in order to help to decide whether someone is on the autism spectrum or not. This guide explains more about the manuals and criteria for an autism diagnosis. 

Diagnostic manuals 

International Classification of Diseases, eleventh edition (ICD-11) 

A new edition of the International Classification of Diseases, the ICD-11, was published in 2022. The ICD-11 replaces the ICD-10 described below. The information on this page will be updated soon, as part of a process to update all our web pages relating to autism diagnosis.

International Classification of Diseases, tenth edition (ICD-10) 

The ICD-10 presents a number of possible autism profiles, such as childhood autism, atypical autism and Asperger syndrome. These profiles are included under the Pervasive Developmental Disorders heading, defined as "A group of disorders characterized by qualitative abnormalities in reciprocal social interactions and in patterns of communication, and by a restricted, stereotyped, repetitive repertoire of interests and activities. These qualitative abnormalities are a pervasive feature of the individual's functioning in all situations". 

Diagnostic and Statistical Manual, fifth edition (DSM-5) 

Although not the most commonly used manual in the UK, DSM-5 is likely to have a significant influence on the next edition of the ICD. This manual has recently been updated and is also used by diagnosticians. 

The diagnostic criteria are clearer and simpler than in the previous version of the DSM, and sensory behaviours are now included. This is useful as many autistic people have sensory differences which affect them on a day-to-day basis. It now includes 'specifiers' to indicate support needs and other factors that impact on the diagnosis. 

Diagnostic criteria 

The DSM-5 Manual defines autism spectrum disorder as “persistent difficulties with social communication and social interaction” and “restricted and repetitive patterns of behaviours, activities or interests” (this includes sensory behaviour), present since early childhood, to the extent that these “limit and impair everyday functioning”. 

In DSM-5, the terms ‘autistic disorder’, ‘Asperger disorder’, ‘childhood disintegrative disorder’ and ‘Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS)’ have been replaced by the collective term 'autism spectrum disorder'. This means that it’s likely that ‘autism spectrum disorder’ (ASD) will become the most commonly given diagnosis.  

Asperger syndrome 

For many people, the term Asperger syndrome is part of their day-to-day vocabulary and identity, so it is understandable that there are concerns around the removal from DMS-5 of Asperger syndrome as a distinct category. Everyone who currently has a diagnosis on the autism spectrum, including those with Asperger syndrome, will retain their diagnosis. No one will ‘lose’ their diagnosis because of the changes in DSM-5. 

Specifiers for autism spectrum disorder 

DSM-5 has introduced specifiers to help the clinician to describe associated or additional conditions, eg intellectual impairment, language impairment, genetic conditions, behavioural disorder, catatonia. 

One of the specifiers relates to the ‘severity’ of social communication impairments and restricted, repetitive patterns of behaviour. There are three levels: requiring support, requiring substantial support, requiring very substantial support. This can allow the clinician to give an indication of how much someone’s condition affects them and how much support an individual needs. 

However, people who receive a diagnosis are not automatically eligible for support. DSM-5 explains that ‘severity’ levels may vary by context and also fluctuate over time, that the descriptive severity categories should not be used to determine eligibility for and provision of services, and that 'these can only be developed at an individual level and through discussion of personal priorities and targets'. 

Social (pragmatic) communication disorder 

The DSM-5 now includes a condition called 'social communication disorder', separate to 'autism spectrum disorder'. This diagnosis would be given where someone exhibits social interaction and social communication difficulties but does not show restricted, repetitive patterns of behaviour, interests or activities.  

Diagnostic tools 

Diagnostic tools including the DISCO (Diagnostic Interview for Social and Communication Disorders), the ADI-R (Autism Diagnostic Interview - Revised), the ADOS (Autism Diagnostic Observation Schedule) and 3Di (Developmental, Dimensional and Diagnostic Interview) are used to collect information in order to help to decide whether someone is on the autism spectrum or not. The ADOS tool differs from the others as it is not based on developmental data and therefore only looks at current behaviour and skills. The criteria form the basis for the diagnosis, but the individual clinician’s judgement is crucial. 

Next steps 

• Read more about diagnostic tools
• Find out about post-diagnostic support
• Find out more about our specialist training for professionals in the diagnosis and assessment of autism.