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Quantitative Checklist for Autism in Toddlers (Q-CHAT). A population screening study with follow-up: the case for
Carrie Allison1, Fiona E Matthews2, Liliana Ruta3
1Psychiatry Department, Autism Research Centre, University of Cambridge, Cambridge, UK.
Insights
The Quantitative Checklist for Autism in Toddlers (Q-CHAT) can identify autism in toddlers, but has a low positive predictive value. Continued surveillance is needed as not all autism cases are detectable in early toddlerhood.
Area of Science:
- Developmental Pediatrics
- Child Psychology
- Screening Tools
Background:
- Early identification of autism spectrum disorder (ASD) is crucial for timely intervention.
- Population screening in toddlers can aid in early detection.
- The Quantitative Checklist for Autism in Toddlers (Q-CHAT) is a tool used for this purpose.
Purpose of the Study:
- To evaluate the test accuracy of the Q-CHAT for autism screening in toddlers aged 18-30 months.
- To assess the positive predictive value (PPV) of the Q-CHAT.
- To determine the utility of the Q-CHAT in a prospective population screening setting.
Main Methods:
- A prospective population screening study involving 13,070 toddlers.
- Screening using the Q-CHAT at 18-30 months, with diagnostic assessments.
- Follow-up at age 4 using the Childhood Autism Spectrum Test (CAST) and Checklist for Referral (CFR).
Main Results:
- The Q-CHAT identified 11 children with autism at phase 1, with a PPV of 17% at a cut-point of 39.
- At phase 2 follow-up, the PPV increased to 28%.
- All children diagnosed with autism at phase 1 also met criteria at phase 2.
Conclusions:
- The Q-CHAT can facilitate early identification and referral for autism diagnosis in toddlers.
- The study highlights a low PPV, indicating a significant number of false positives.
- The findings underscore the importance of continued surveillance and rescreening due to the emergence of new cases and the limitations of early detection.
Objective:
This is a prospective population screening study for autism in toddlers aged 18-30 months old using the Quantitative Checklist for Autism in Toddlers (Q-CHAT), with follow-up at age 4.
Design:
Observational study.
Setting:
Luton, Bedfordshire and Cambridgeshire in the UK.
Participants:
13 070 toddlers registered on the Child Health Surveillance Database between March 2008 and April 2009, with follow-up at age 4; 3770 (29%) were screened for autism at 18-30 months using the Q-CHAT and the Childhood Autism Spectrum Test (CAST) at follow-up at age 4.
Interventions:
A stratified sample across the Q-CHAT score distribution was invited for diagnostic assessment (phase 1). The 4-year follow-up included the CAST and the Checklist for Referral (CFR). All with CAST ≥15, phase 1 diagnostic assessment or with developmental concerns on the CFR were invited for diagnostic assessment (phase 2). Standardised diagnostic assessment at both time-points was conducted to establish the test accuracy of the Q-CHAT.
Main Outcome Measures:
Consensus diagnostic outcome at phase 1 and phase 2.
Results:
At phase 1, 3770 Q-CHATs were returned (29% response) and 121 undertook diagnostic assessment, of whom 11 met the criteria for autism. All 11 screened positive on the Q-CHAT. The positive predictive value (PPV) at a cut-point of 39 was 17% (95% CI 8% to 31%). At phase 2, 2005 of 3472 CASTs and CFRs were returned (58% response). 159 underwent diagnostic assessment, including 82 assessed in phase 1. All children meeting the criteria for autism identified via the Q-CHAT at phase 1 also met the criteria at phase 2. The PPV was 28% (95% CI 15% to 46%) after phase 1 and phase 2.
Conclusions:
The Q-CHAT can be used at 18-30 months to identify autism and enable accelerated referral for diagnostic assessment. The low PPV suggests that for every true positive there would, however, be ~4-5 false positives. At follow-up, new cases were identified, illustrating the need for continued surveillance and rescreening at multiple time-points using developmentally sensitive instruments. Not all children who later receive a diagnosis of autism are detectable during the toddler period.
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