What are the recommended screening tools for autism spectrum disorder (Autism)

Recommended Screening Tools for Autism Spectrum Disorder

The Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F) is the most strongly recommended screening tool for ASD, with universal screening recommended at 18 and 24 months of age. 1, 2

Primary Screening Tool: M-CHAT-R/F

The M-CHAT-R/F should be used as the first-line screening instrument for children aged 16-30 months, with a two-step protocol that includes an initial questionnaire followed by a structured follow-up interview for positive screens. 1, 3

Scoring and Risk Stratification

The M-CHAT-R/F uses a three-level risk algorithm that maximizes clinical utility: 1

• Low risk (0-2 points): No further action needed
• Medium risk (3-6 points): Requires follow-up telephone interview
• High risk (≥7 points): Immediate referral for diagnostic evaluation and early intervention without waiting for follow-up interview 1

Performance Characteristics

The M-CHAT-R/F demonstrates strong overall diagnostic accuracy: 4, 5

• Pooled sensitivity: 82.6-83% 4, 5
• Pooled specificity: 45.7-94% (varies by population and use of follow-up interview) 4, 5
• Positive Predictive Value (PPV):
  • Low-risk populations with follow-up: 51.2-65% 1, 4
  • High-risk populations with follow-up: 75.6-76% 1, 4
  • Without follow-up interview: PPV drops dramatically to 5.8% in low-risk samples 6

Critical Implementation Details

The follow-up telephone interview is essential and significantly improves specificity—never skip this step for medium-risk scores. 6, 1 The original M-CHAT without structured follow-up had unacceptably low PPV (5.8%), which improved to 43-65% with the follow-up component. 6, 1

Age at screening affects performance: 2

• Younger children (16-23 months): PPV = 28%
• Older children (24-30 months): PPV = 61% 2

Despite lower specificity at 18 months, screening at this age remains valuable because the PPV for any diagnosable developmental disorder is high, ensuring children who need intervention are identified. 2

Alternative and Supplementary Screening Tools

Level 2 Screening Tools (For High-Risk or Referred Children)

Screening Tool for Autism in Two-Year-Olds (STAT): 3

• Designed for children aged 14-36 months already referred for developmental concerns
• Sensitivity: 92%, Specificity: 85% in clinical samples 3
• Use as a level 2 screener after positive M-CHAT-R/F or when developmental concerns exist 3

Quantitative Checklist for Autism in Toddlers (Q-CHAT): 6, 3

• Shows promise with sensitivity 91% and specificity 89% in case-control samples 3
• Requires additional validation in community-based samples before routine clinical use 6

Tools NOT Recommended

Checklist for Autism in Toddlers (CHAT): 6, 3

• Do not use—sensitivity is only 18% 6, 3
• Misses 82% of children with ASD 6

Special Population Considerations

High-Risk Siblings

Children with siblings diagnosed with ASD require intensified surveillance with screening at minimum at both 18 and 24 months, as their risk is 14-18% compared to the general population risk of 1-2%. 3, 2

For these children: 2

• Conduct continuous developmental surveillance at all well-child visits
• Use M-CHAT-R/F at 18 and 24 months minimum
• Consider additional screening if any developmental concerns arise between scheduled screenings 2

Clinical Workflow Algorithm

1. At 18-month well-child visit: Administer M-CHAT-R/F to all children 1, 2

   • Score 0-2: Routine surveillance continues
   • Score 3-6: Conduct follow-up telephone interview
   • Score ≥7: Immediate referral for diagnostic evaluation 1

2. At 24-month well-child visit: Repeat M-CHAT-R/F screening for all children 1, 2

   • Use same scoring algorithm as above
   • Higher PPV at this age (61% vs 28% at younger ages) 2

3. For positive screens after follow-up interview (score ≥2 on follow-up): 1

   • Refer immediately for comprehensive diagnostic evaluation
   • Refer simultaneously for early intervention services—do not wait for diagnosis 2

Common Pitfalls and Caveats

Counseling families about positive screens requires acknowledging the moderate PPV—approximately 50-60% of screen-positive children in low-risk populations will ultimately receive an ASD diagnosis. 4 This means roughly half of positive screens are false positives, often representing other developmental concerns that still warrant evaluation. 1

The U.S. Preventive Services Task Force notes insufficient evidence to assess the balance of benefits and harms of universal screening in children for whom no concerns have been raised, though the American Academy of Pediatrics still recommends universal screening at 18 and 24 months. 1, 2 This reflects ongoing debate about universal versus targeted screening, but current practice guidelines favor universal screening. 2

False positives may occur due to developmental concerns that resolve over time and because behaviors in typically developing toddlers can overlap with ASD deficits. 1 However, even when ASD is not ultimately diagnosed, these children often have other developmental needs requiring intervention. 2

Never use the M-CHAT-R/F without the follow-up interview component for medium-risk scores—this is the most common implementation error and dramatically reduces specificity. 6, 1