From the Guidelines
Autism Spectrum Disorder (ASD) is primarily diagnosed through comprehensive behavioral and developmental assessments, with genetic testing and other medical evaluations playing a supportive role in identifying underlying causes or associated conditions. The diagnostic process for ASD involves a multidisciplinary approach, including developmental pediatricians, child psychologists, speech-language pathologists, and neurologists, who assess the child's developmental history and current behaviors using standardized screening instruments such as the Modified Checklist for Autism in Toddlers (M-CHAT), the Autism Diagnostic Observation Schedule (ADOS-2), and the Autism Diagnostic Interview-Revised (ADI-R) 1.
Diagnostic Tools and Process
The primary diagnostic tools evaluate social communication, interaction patterns, and restricted or repetitive behaviors. Parents should expect direct observation of the child, detailed interviews about developmental milestones, and questionnaires about behavior patterns. Early screening often begins during regular pediatric check-ups, with more specialized assessments following if concerns arise.
Role of Genetic Testing
While genetic testing, such as chromosomal microarray (CMA) and fragile X testing, may be used to rule out other conditions or identify associated genetic syndromes, these are not diagnostic for ASD itself 1. The yield of genetic testing in the presence of clinical suspicion is currently in the range of at least one third of cases. Recent guidelines suggest that exome sequencing (ES) or whole genome sequencing (WGS) should be considered as a first- or second-tier test in all patients with unexplained developmental delay (DD) or intellectual disability (ID) 1.
Comprehensive Assessment
A comprehensive assessment for ASD includes medical, psychological, communication, and occupational evaluations to identify areas of strength and weakness, which are useful in designing intervention programs. This approach ensures that the diagnosis and subsequent management plan are tailored to the individual's specific needs, improving outcomes in terms of morbidity, mortality, and quality of life.
Current Recommendations
Current recommendations from professional societies, such as the American Academy of Pediatrics (AAP) and the American Academy of Child and Adolescent Psychiatry (AACAP), emphasize the importance of a comprehensive and multidisciplinary assessment for children with suspected ASD, which may include genetic testing as part of the evaluation process to rule out other conditions or identify genetic causes 1. However, the diagnosis of ASD is based on behavioral criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), focusing on persistent deficits in social communication and interaction alongside restricted, repetitive patterns of behavior, interests, or activities.
From the Research
Diagnostic Tests for Autism Spectrum Disorder (ASD)
There are several diagnostic tests used to diagnose Autism Spectrum Disorder (ASD), including:
- Autism Diagnostic Interview-Revised (ADI-R) 2, 3, 4
- Autism Diagnostic Observation Schedule (ADOS) 2, 3, 5, 6, 4
- Childhood Autism Rating Scale (CARS) 3
- Gilliam Autism Rating Scale (GARS) 3
- Diagnostic Interview for Social and Communication Disorder (DISCO) 3
- Developmental, Dimensional, and Diagnostic Interview (3di) 3
Characteristics of Diagnostic Tests
The characteristics of these diagnostic tests are as follows:
- ADI-R: a semi-structured interview that assesses social interaction, communication, and play 2, 4
- ADOS: a semi-structured observation that assesses social interaction, communication, and play 2, 5, 6, 4
- CARS: a rating scale that assesses social interaction, communication, and behavior 3
- GARS: a rating scale that assesses social interaction, communication, and behavior 3
- DISCO: a diagnostic interview that assesses social interaction and communication 3
- 3di: a diagnostic interview that assesses social interaction, communication, and behavior 3
Effectiveness of Diagnostic Tests
The effectiveness of these diagnostic tests varies, with:
- ADI-R and ADOS having the largest evidence base and highest sensitivity and specificity 2
- ADOS having a summary sensitivity of 0.94 and summary specificity of 0.80 3
- CARS having a summary sensitivity of 0.80 and summary specificity of 0.88 3
- ADI-R having a summary sensitivity of 0.52 and summary specificity of 0.84 3
Limitations of Diagnostic Tests
The limitations of these diagnostic tests include:
- ADI-R and ADOS may not be effective in differentiating between autism and other disorders, such as schizophrenia 4
- ADOS may have lower diagnostic accuracy in women, the elderly, and individuals with higher intellectual abilities 4
- CARS and GARS may have lower sensitivity and specificity compared to ADI-R and ADOS 3