Diagnostic Guidelines for Autism Spectrum Disorder
The diagnosis of Autism Spectrum Disorder (ASD) requires a comprehensive evaluation by a trained professional using objective criteria and standardized tools, with confirmation of diagnosis being critically important before initiating any genetic evaluation or treatment. 1 A tiered, systematic approach to diagnosis is recommended to ensure accurate identification and appropriate intervention planning.
Pre-Evaluation and Initial Assessment
Confirmation of Diagnosis
- Diagnosis must be made by a professional trained in autism diagnosis
- Use of objective criteria and standardized assessment tools is essential
- Complete audiogram required to rule out significant hearing loss
- Cognitive testing should be performed
- Electroencephalogram if clinical suspicion of seizures exists
- Verification of newborn screening results
Early Signs and Symptoms (First 2 Years)
- No response to name when called
- Limited or no use of gestures in communication
- Lack of imaginative play
- Avoidance of eye contact
- Excessive fear
- Lack of interactive play 2, 3
Diagnostic Process
Primary Care Physician's Role
- Often first to raise question of ASD diagnosis
- May diagnose ASD depending on training/comfort level
- Should refer to specialists when needed
- Should obtain high-resolution chromosome studies and Fragile X studies when ASD diagnosis is confirmed 1
Diagnostic Tools
- First-line standardized measures:
- Autism Diagnostic Observation Schedule-Second Edition (sensitivity 91%, specificity 76%)
- Autism Diagnostic Interview (sensitivity 80%, specificity 72%) 2
- Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F)
- Social Communication Questionnaire (SCQ)
- Childhood Autism Rating Scale (CARS) 3
Recommended Evaluation Model
- Interdisciplinary team approach has been shown to be most effective:
- Allows for diagnostic determination in 90% of patients in a single day
- Results in higher rates of patient follow-up care
- Demonstrates higher provider satisfaction
- More cost-effective than psychology-led multidisciplinary evaluations 4
Tiered Diagnostic Evaluation
First Tier
- Examination with special attention to dysmorphic features (including Woods lamp evaluation)
- Targeted testing if specific diagnosis is suspected
- Rubella titers if clinical indicators present
- Standard metabolic screening if clinical indicators present
- Urine mucopolysaccharides and organic acids
- Serum lactate, amino acids, ammonia, and acyl-carnitine profile
- High-resolution chromosomal analysis
- DNA testing for Fragile X 1
Second Tier
- Fibroblast karyotype if leukocyte karyotype is normal and clonal pigmentary abnormalities are noted
- Comparative genomic hybridization (chromosomal microarray)
- MECP2 gene testing (females only)
- PTEN gene testing (if head circumference is 2.5 SD greater than mean) 1
Third Tier
- Brain magnetic resonance imaging
- Serum and urine uric acid testing
- Additional specialized testing based on clinical findings 1
Treatment Options
Behavioral Interventions
- First-line therapy for ASD consists of intensive behavioral interventions
- Early Start Denver Model is beneficial in children 5 years or younger
- Improves language, play, and social communication (small to medium effect size) 2
Pharmacological Treatment
- Indicated only for co-occurring psychiatric conditions
- Risperidone is FDA-approved for treatment of irritability associated with autistic disorder in children and adolescents (ages 5-17 years)
- Aripiprazole can also improve irritability and aggression (large effect size)
- Psychostimulants are effective for comorbid ADHD (moderate effect size) 2
Common Comorbidities to Assess
Individuals with ASD have higher rates of:
- Depression (20% vs 7% in general population)
- Anxiety (11% vs 5%)
- Sleep difficulties (13% vs 5%)
- Epilepsy (21% with co-occurring intellectual disability vs 0.8%) 2
Important Considerations and Pitfalls
Diagnostic Challenges
- Risk of overdiagnosis or misdiagnosis leading to unnecessary interventions
- Many neurodevelopmental disorders have overlapping phenotypes
- Diagnostic process can be lengthy, complex, and emotionally challenging for families 1, 3
Wait Times
- Maximum wait time of 3-6 months is recommended
- Actual wait times often exceed one year in many communities
- More pediatric healthcare providers should be trained to diagnose less complex cases 6
Medication Side Effects
- Common adverse effects include changes in appetite, weight, and sleep
- Tardive dyskinesia reported in 0.1% of children and adolescents treated with risperidone
- Weight gain is common (33% of risperidone-treated patients had >7% weight gain) 5
Benefits of Early Diagnosis
- Enables timely intervention, improving developmental outcomes
- Allows access to appropriate support services and educational resources
- Facilitates better coping mechanisms for families 3