BACKGROUND Autism is the most common clinical developmental disorder in children. The childhood autism rating scale (CARS) and autistic autism behavior checklist (ABC) are the most commonly used assessment scales for diagnosing autism. However, the diagnostic validations and the corresponding cutoffs for CARS and ABC in individuals with suspected autism spectrum disorder (ASD) remain unclear. Furthermore, for suspected ASD in China, it remains unclear whether CARS is a better diagnostic tool than ABC. Also unclear is whether the current cutoff points for ABC and CARS are suitable for the accurate diagnosis of ASD. AIM To investigate the diagnostic validity of CARS and ABC based on a large Chinese sample. METHODS A total of 591 outpatient children from the ASD Unit at Beijing Children’s Hospital between June and November 2019 were identified. First, the Clancy autism behavior scale (CABS) was used to screen out suspected autism from these children. Then, each suspected ASD was evaluated by CARS and ABC. Receiver operating characteristic (ROC) curve analysis was used to compare diagnostic validations. We also calculated the area under the curve (AUC) for both CARS and ABC. RESULTS We found that the Cronbach alpha coefficients of CARS and ABC were 0.772 and 0.426, respectively. Therefore, the reliability of the CARS was higher than that of the ABC. In addition, we found that the correlation between CARS and CABS was 0.732. Next, we performed ROC curve analysis for CARS and ABC, which yielded AUC values of 0.846 and 0.768, respectively. The cutoff value, which is associated with the maximum Youden index, is usually applied as a decision threshold. We found that the cutoff values of CARS and ABC were 34 and 67, respectively. CONCLUSION This result indicated that CARS is superior to ABC in the Chinese population with suspected ASD.

Autism is the most common clinical developmental disorder in children. The Childhood Autism Rating Scale (CARS) and Autistic Behavior Checklist (ABC) are the most commonly used assessment scales for diagnosing autism. The aim of this study is to compare the diagnostic validities of CARS and ABC based on a large Chinese sample. A total of 474 children with suspected autism spectrum disorder (ASD) were screened by CARS and ABC. Receiver operating characteristic (ROC) curve analysis was performed and it showed that the area-under-the-curve values of CARS is higher than ABC significantly (p < 0.05) and the suggested cutoff values of CARS and ABC were 34 and 67, respectively. It indicated that CARS is superior to ABC in the Chinese population with suspected ASD.