The Childhood Autism Spectrum Test (CAST) As a Screener for High-Functioning Children, Adolescents, and Young Adults with Autism Spectrum Disorder

Background: Screening older children, adolescents, and adults for an Autism Spectrum Disorder (ASD) diagnosis may be challenging, due to characteristics being masked by learned strategies, as well as the existence of psychiatric co-morbidities. Therefore, the use of a screener examining the existence of diagnostic features at an earlier age, when these are more crystalized, may assist in referring relevant applicants for a thorough diagnostic assessment.

This study evaluated The Childhood Autism Spectrum Test (CAST, Scott et al., 2002), as a parent-report screener with children in the age group it was originally designed for (6-11), as well as with adolescents (aged 12-17) and adults (aged 18-46), whose parents were asked to report on their behavior during primary school years.

Objectives: To evaluate the stability of the CAST as a screener in three age groups, and to report on its psychometric properties in an Israeli sample.

Methods: Parents of 43 individuals (15 children, 11 adolescents,17 adults), who were diagnosed with ASD by professional clinicians using the ADI-R (Lord et al., 1994) and the ADOS-G (Lord et al., 2000), filled out the CAST as part of their assessment process at an ASD clinic. In addition, a group of 101 parents of individuals from the general population (parents of 35 children, 30 adolescents and 36 adults) matched on child's age and gender filled out the CAST electronically.

Results: the clinical group scored significantly higher on the CAST (M=17.04, SD=5.93), compared to the general population group (M=6.18, SD=4.02), with no significant differences between age groups and no diagnosis by age-group interaction. A cutoff score of 13, two points lower than the original cutoff (Scott et. al., 2002) yielded sensitivity of 0.84 and specificity of 0.86. Internal consistency for the CAST was α=0.9, with sub-scales' internal consistency ranging between 0.63-0.79. Discriminant analysis revealed the accuracy of prediction using all CAST items was 90%. In addition, the CAST distinguished between participants diagnosed with ASD and participants in the general-population group, whose parents reported they have an ADHD diagnosis.

Conclusions: Parental report on childhood behavior using the CAST may serve as a good screener for children, as well as for adolescents and adults with ASD. Our preliminary results also suggest the CAST discriminates well between individuals with ASD and those with ADHD. This finding may be of importance due to diagnostic overlaps between the two conditions in higher-functioning individuals.