The criterion-related validity of the Childhood Autism Rating Scale and the Autism Behavior Checklist

The present study sought to examine the relationship between two popular instruments for screening autistic children: the Childhood Autism Rating Scale (CARS) and the Autism Behavior Checklist (ABC). The sample included 77 individuals. The records of 48 subjects contained firm diagnoses of autism, while the suggestion of autism was found in the remaining records. Correlations between the two scales ranged from -.16 to .73 (median = .39). The validity coefficient between the two total scores was .67. Using cutoff scores recommended by the authors, an analysis of the sensitivity of the two instruments was conducted. The CARS correctly identified 98% of the autistic subjects; it identified 69% of the possibly autistic as autistic. The ABC correctly identified 88% of the autistic subjects, while it identified 48% of those subjects considered possibly autistic as autistic. A phi coefficient was computed to estimate the degree of relationship between the nominal classifications produced by the two instruments. A moderate relationship was found (r phi = .54). Implications of the results are discussed.