How do you diagnose autism spectrum disorder (ASD) in a child?

Diagnosing Autism Spectrum Disorder in Children

The diagnosis of autism spectrum disorder (ASD) in children requires a comprehensive multidisciplinary assessment that evaluates social communication deficits and restricted, repetitive behaviors using standardized diagnostic tools such as the Autism Diagnostic Observation Schedule (ADOS) and Autism Diagnostic Interview-Revised (ADI-R). 1

Early Signs and Symptoms (12-24 months)

Early identification of ASD is crucial for timely intervention. Key markers between 12-24 months include:

• Reduced social attention and social communication 1
• Increased repetitive behaviors with objects 1
• Abnormal body movements and temperament dysregulation 1
• Failure to respond to name when called 1, 2
• Limited or absent use of gestures in communication 2
• Lack of imaginative play 2, 3
• Decreased eye contact 1, 3
• Lower positive affect and higher negative affect 1
• Difficulty controlling behavior 1

Diagnostic Process

Step 1: Screening

• Use validated screening tools during well-child visits at 18 and 24 months 1, 4
• Modified Checklist for Autism in Toddlers (M-CHAT) and its revisions (M-CHAT-F, M-CHAT-R/F) are commonly used parent-rated scales 1, 5, 3
• Positive screening results should prompt referral for comprehensive evaluation 1

Step 2: Comprehensive Diagnostic Evaluation

• Standard psychiatric assessment including interviews with child and family 1
• Review of developmental history and past records 1
• Systematic observation of social interaction and restricted/repetitive behaviors 1
• Assessment using standardized diagnostic tools:
  • Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) (sensitivity 91%, specificity 76%) 2
  • Autism Diagnostic Interview-Revised (ADI-R) (sensitivity 80%, specificity 72%) 2
  • Childhood Autism Rating Scale (CARS) 3

Step 3: Multidisciplinary Assessment

• Medical assessment including:
  • Physical examination 1
  • Hearing screen 1
  • Wood's lamp examination for tuberous sclerosis 1
  • Genetic testing (G-banded karyotype, fragile X testing, chromosomal microarray) 1
• Psychological assessment of cognitive ability and adaptive skills 1
• Communication assessment of receptive/expressive language and pragmatic skills 1
• Occupational and physical therapy evaluations for sensory/motor difficulties 1

Common Pitfalls and Caveats

• Diagnostic Delay: ASD is typically not diagnosed until 3-4 years of age despite parents often expressing concerns by 18 months 1
• Heterogeneity: ASD presents with tremendous clinical diversity in etiology, neurobiology, onset, and course 1
• Variable Presentation: Some children show behavioral differences from early infancy, while others develop typically before showing regression in the second year 1
• Comorbidities: Children with ASD have higher rates of depression (20%), anxiety (11%), sleep difficulties (13%), and epilepsy (21% with co-occurring intellectual disability) 2
• Diagnostic Barriers: Long wait lists for specialist evaluations and limited workforce create substantial delays in diagnosis 6

Improving Diagnostic Access

• Consider tiered diagnostic approaches where pediatric primary care providers can diagnose clear cases and refer complex ones to specialists 6
• Coordinate between healthcare providers to reduce diagnostic delays that impede access to early intervention 6
• Recognize that early diagnosis enables access to specialized interventions, support services, and educational resources 3

After Diagnosis

• Early intensive behavioral interventions based on applied behavior analysis improve cognitive ability, language, and adaptive skills 4
• Multidisciplinary treatment approaches may include:
  • Behavioral interventions (Applied Behavior Analysis, Early Start Denver Model) 5, 2
  • Speech-language therapy 5
  • Occupational therapy and sensory integration 5
  • Pharmacotherapy for co-occurring conditions when indicated 2