Diagnostic Tools and Approaches for Autism Spectrum Disorder

Age-Specific Screening Tools

The American Academy of Pediatrics recommends the Modified Checklist for Autism in Toddlers (M-CHAT) as a level 1 and level 2 screening tool for children under 24 months, with strong evidence supporting its use 1, 2
The Communication and Symbolic Behavior Scales Developmental Profile (CSBS DP) Infant/Toddler Checklist is effective for detecting communication delays that may indicate ASD by the first birthday, though not specific for ASD 3
The Quantitative Checklist for Autism in Toddlers (Q-CHAT) shows promise with preliminary data suggesting high sensitivity (91%) and specificity (89%) in case-control samples 1
The Screening Tool for Autism in Two-Year-Olds (STAT) is a level 2 screener with sensitivity and specificity as high as 92% and 85% respectively in clinical samples of 2-year-olds 3, 4
The Systematic Observation for Red Flags shows promise in discriminating ASD from other communication delays with a positive predictive value of 0.75 for detecting toddlers with ASD or developmental delay 3

The American College of Medical Genetics recommends a tiered evaluation approach, including initial examination, high-resolution chromosomal analysis, and DNA testing for Fragile X as the first tier 5
The second tier of evaluation should include comparative genomic hybridization (chromosomal microarray), MECP2 gene testing (females only), and PTEN gene testing (if head circumference is 2.5 SD greater than mean) 5
The third tier of evaluation should include brain MRI and metabolic testing as indicated 5

Siblings of children with ASD are at elevated risk (14-18%) and require intensified surveillance with screening at 18 and 24 months of age 3, 4
The diagnostic stability of ASD in children aged ≥24 months is well established, though diagnosis before 24 months may have higher false-positive rates 4

The CHAT (original version) has low sensitivity (18%) and is not recommended for current early detection efforts 1