Social but Not Repetitive Scores on the Quantitative Checklist for Autism in Toddlers (Q-CHAT) Predict Later Autism Spectrum Diagnosis in a Prospective High-Risk Sibling Study

Background: The British Autism Study of Infant Siblings (BASIS) is a prospective study of children with older siblings with ASD (High-Risk sibs: HR) and controls with older siblings who are developing typically (Low-Risk sibs: LR). Participants are assessed at various time points from approximately 5 months until 36 months of age. The Q-CHAT is a 25-item parent questionnaire, designed to be an early screening instrument for autism. Each item has a 5-point Likert scale, with scores ranging from 0 to 4. Higher scores relate to higher levels of autism symptomatology.

Objectives: To investigate the factor structure of the Q-CHAT in a sample of 24-month-olds participating in a prospective study of children at risk for ASD, and to determine which factors, if any, are predictive of outcome, and at what ages.

Methods: The Q-CHAT was completed by parents when their children were 14-, 24- and 36-months of age. Following the 36-month visit a best estimate research diagnosis was applied to HR sibs. Outcome categories are: Typically developing (HR-TD); ASD (HR-ASD) and Atypical (HR-ATYP). The latter group consists of children not meeting criteria for ASD but meeting ASD criteria on the ADOS, ADI-R or being below 1.5 SD on the Mullen. Principal Component Analysis (PCA) was conducted on the 24-month Q-CHAT scores.

Results: Q-CHAT scores were available for 218 children. PCA suggested a two-factor solution. Factor A, Social Communication (SC), has 8 items, and Factor B, Stereotyped and Repetitive Behaviours (SRB), 9 items. Outcomes were known for 182 children: LR (N=69); HR-TD (N=67); HR-ATYP (N=22); HR-ASD (N=24). At 14 months SC scores predicted ASD outcome (t=3.61, p<.001) but the SRB factor did not (t=-1.42, p=.17). In fact, the LR scores for SRB were significantly higher than for the combined HR group scores (t=-2.76, p=.007). At 14 months the two factors were not significantly correlated (r=.02, p=.79). At 24 months SC was significantly higher in the HR-ASD group than the combined non-ASD groups (t=4.23, p<.001), but differences were not significant for SRB (t=1.96, p=.06). SRB scores for LR and HR groups did not differ significantly. At 36 months both factors were significantly higher in the ASD group than in the non-ASD groups (SC: t=4.18, p<.001; SRB: t=3.27, p=.003).

Conclusions: Findings suggest that differences in parent-reported social communication skills in children during their second and third years may be predictive of later autism diagnostic status. For stereotyped and repetitive behaviours, however, there seems to be a more dynamic situation, with differences in early ratings not predicting outcome but by 36 months scores differed in the expected pattern. This shift appears to be due to a combination of two issues: children who are on their way to developing autism may show more stereotyped and repetitive behaviours over time; and parents with no direct experience of autism may rate their young children as having more repetitive behaviours relative to parents of children with older siblings with autism.