What are the changes in the diagnosis of Autism Spectrum Disorder (ASD) across Diagnostic and Statistical Manual of Mental Disorders (DSM) versions 3, 3-TR (Text Revision), 4, 5, and 5-TR (Text Revision), and International Classification of Diseases (ICD) versions 10 and 11?

Evolution of Autism Spectrum Disorder Diagnostic Criteria Across DSM and ICD Versions

DSM-III to DSM-IV Era: The Pervasive Developmental Disorders Framework

The earlier DSM versions (DSM-III, DSM-III-R, and DSM-IV) classified autism under "Pervasive Developmental Disorders" (PDD), which included separate diagnostic entities: Autistic Disorder, Asperger's Disorder, and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS). 1, 2

Key Features of DSM-IV Classification:

• Three distinct domains of impairment were required: social interaction deficits, communication impairments, and restricted/repetitive behaviors 2
• Language delay was emphasized as a diagnostic criterion, particularly for differentiating Autistic Disorder from Asperger's Disorder 2
• Age of onset was specified, requiring symptoms to be present before age 3 years 2
• Separate categorical diagnoses allowed clinicians to distinguish between Autistic Disorder, Asperger's Disorder, and PDD-NOS based on severity and language functioning 1

DSM-5 (2013): The Paradigm Shift to Autism Spectrum Disorder

DSM-5 eliminated the separate PDD subcategories and consolidated them into a single diagnosis of Autism Spectrum Disorder, fundamentally restructuring the diagnostic approach. 1, 2

Major Structural Changes:

• Collapsed three symptom domains into two: (1) social communication/interaction deficits and (2) restricted, repetitive patterns of behavior, interests, or activities 3, 2
• Eliminated Asperger's Disorder and PDD-NOS as distinct diagnostic entities, subsuming them under the umbrella term ASD 1, 3
• Removed language delay as a core criterion, recognizing that language impairment is not universal in autism 2
• Modified age of onset requirements: symptoms must be present in early childhood, but the disorder may be diagnosed later in life when social demands exceed capacities 2

Introduction of Severity Specifiers:

DSM-5 introduced a three-level severity rating system (Levels 1,2, and 3) that must be specified separately for both core symptom domains. 4, 5

• Level 1 ("requiring support"): Deficits cause noticeable impairments; inflexibility causes significant interference in one or more contexts 5
• Level 2 ("requiring substantial support"): Marked deficits in social communication; inflexibility interferes with functioning in a variety of contexts 5
• Level 3 ("requiring very substantial support"): Severe deficits; inflexibility markedly interferes with functioning in all spheres 5

Each domain (social communication and restricted/repetitive behaviors) is rated separately, allowing for different severity levels across the two domains. 5

DSM-5-TR (Text Revision): Refinements Without Structural Changes

DSM-5-TR maintained the core diagnostic structure of DSM-5 but provided clarifications and updated clinical guidance. 4

Key Refinements:

• Emphasized the importance of specifying severity levels for treatment planning and monitoring progress over time 4
• Clarified that severity specifiers must account for both current presentation and response to intervention, considering historical symptoms that may not be currently present due to intervention or development 5
• Strengthened recommendations for comprehensive assessment, including intellectual functioning evaluation, adaptive behavior assessment, and documentation of peer interactions across contexts 4

ICD-10: The International Perspective

ICD-10 maintained a classification system similar to DSM-IV, with separate diagnostic categories under "Pervasive Developmental Disorders." 6, 7

ICD-10 Structure:

• Retained distinct categories including Childhood Autism, Atypical Autism, and Asperger Syndrome 7
• Used similar three-domain criteria as DSM-IV for core symptom assessment 6
• Served as the worldwide general medical classification system while DSM-IV/5 was primarily used in the United States 6

ICD-11 (2022): Harmonization with DSM-5

ICD-11, implemented January 2022, underwent the largest and most participative revision process in mental health classification history, with three major aims: global applicability, scientific validity, and clinical utility. 8, 3

Structural Reorganization:

• Expanded from 11 to 21 disorder groupings in the Mental, Behavioral or Neurodevelopmental Disorders (MBND) chapter 8
• Eliminated the separate grouping for disorders with onset in childhood and adolescence, moving these disorders to other groupings to highlight developmental continuity across the lifespan 8
• Harmonized with DSM-5 structure while maintaining ICD's broader medical classification purpose 8, 6

Diagnostic Approach:

• Adopted a dimensional approach within a categorical system, similar to DSM-5's severity specifiers 8
• Maintained categorical classification based on self-reported or clinically observable symptoms, with both ICD-10 and ICD-11 remaining fundamentally categorical systems 8
• Introduced stepwise diagnostic approaches for some categories, incorporating both categorical and dimensional elements 8

Evidence for Improved Performance:

Field studies provide preliminary evidence that ICD-11 demonstrates higher reliability and clinical utility compared with ICD-10. 8

Introduction of Social (Pragmatic) Communication Disorder

A critical consequence of DSM-5 changes was the creation of Social (Pragmatic) Communication Disorder (SPCD) as a new diagnostic entity for individuals with social communication deficits without restricted/repetitive behaviors. 1, 7

SPCD Characteristics:

• Addresses individuals who would have previously received PDD-NOS diagnoses but do not meet full ASD criteria under DSM-5 1, 7
• Focuses on pragmatic language impairment without the behavioral domain requirements of ASD 1, 7
• Similar changes are reflected in ICD-11's approach to pragmatic language impairment 7

Clinical Implications and Concerns:

The reclassification of some individuals from PDD-NOS to SPCD raised concerns about potential restrictions in service eligibility, particularly for early intervention programs under IDEA. 1

• Children with SPCD diagnoses may have limited access to intensive behavioral interventions, inclusive group placements, and family support services that are typically available for ASD diagnoses 1
• Service authorization may be restricted to speech-language therapy rather than the multi-disciplinary intensive services required 1

Common Pitfalls and Clinical Considerations

Assessment Requirements Across Versions:

Regardless of DSM or ICD version, comprehensive assessment must include direct observation using standardized tools like the Autism Diagnostic Observation Schedule (ADOS), evaluation of intellectual functioning, adaptive behavior assessment, and documentation across multiple contexts. 4, 9

Comorbidity Screening:

Systematic screening for comorbid conditions including ADHD, anxiety disorders, depression, learning disorders, and sleep disorders is essential across all diagnostic frameworks. 9

Differential Diagnosis Challenges:

When evaluating social communication difficulties, clinicians must carefully differentiate between ASD and SPCD by thoroughly assessing for restricted, repetitive patterns of behavior, as this distinction fundamentally affects treatment planning and service eligibility. 9, 7