Re-adjusting the cut-off score of the Korean version of the Childhood Autism Rating Scale for high-functioning individuals with autism spectrum disorder.

AIM: The current cut-off score of the Korean version of the Childhood Autism Rating Scale (K-CARS) does not seem to be sensitive enough to precisely diagnose high-functioning autism. The aim of this study was to identify the optimal cut-off score of K-CARS for diagnosing high-functioning individuals with autism spectrum disorders (ASD).

METHODS

A total of 329 participants were assessed by the Korean versions of the Autism Diagnostic Interview - Revised (K-ADI-R), Autism Diagnostic Observation Schedule (K-ADOS), and K-CARS. IQ and Social Maturity Scale scores were also obtained.

RESULTS

The true positive and false negative rates of K-CARS were 77.2% and 22.8%, respectively. Verbal IQ (VIQ) and Social Quotient (SQ) were significant predictors of misclassification. The false negative rate increased to 36.0% from 19.8% when VIQ was >69.5, and the rate increased to 44.1% for participants with VIQ > 69.5 and SQ > 75.5. In addition, if SQ was >83.5, the false negative rate increased to 46.7%, even if the participant's VIQ was ≤69.5. Optimal cut-off scores were 28.5 (for VIQ ≤ 69.5 and SQ ≤ 75.5), 24.25 (for VIQ > 69.5 and SQ > 75.5), and 24.5 (for SQ > 83.5), respectively.

CONCLUSION

The likelihood of a false negative error increases when K-CARS is used to diagnose high-functioning autism and Asperger's syndrome. For subjects with ASD and substantial verbal ability, the cut-off score for K-CARS should be re-adjusted and/or supplementary diagnostic tools might be needed to enhance diagnostic accuracy for ASD.