The Autism Behavior Checklist (ABC) was designed to offer a method to more objectively identify autism in children. The scale utilizes an observer’s rating of the child’s behavior to quantify behaviors typically associated with Autism.
The ABC was developed as a clinical measure to screen for autism in individuals 3–35-years-of-age. The scale was developed in 1980 and has not undergone revision since then. The ABC consists of 57 item and 5 scales (1) Sensory, (2) Relating, (3) Body and Object use, (4) Language and (5) Social and Self-help .
The items included in the ABC were grouped on the five subscales primarily based on face validity. The items themselves were chosen from many sources, including Kanner’s  article which first outlined autism and Lovaas et al.  work on autism.. After items were written and finalized, internationally recognized experts in the field of autism were asked to provide feedback for the scale. The last stage of scale construction involved sending the scale to 3,000 special education professionals. After feedback from these professionals, weights were then assigned to the individual items .
The ABC total score is used to determine the likelihood of autism. Higher scores indicate the presence of more behaviors consistent with autism. The authors of the ABC assigned individual items a weight of 1–4 according to that behavior’s relevance to autism. A total raw score of 68 or higher is used as a cut-off for indicating a high probability of autism, whereas a score between 53 and 67 indicates questionable autism, and scores of 53 or lower are considered unlikely to indicate autism. This score corresponds with one-half a standard deviation below the mean of children with autism who were included in the standardization sample .
Several researchers have conducted factor analyzes of the ABC to check for the content validity of the scales with mixed results . In these studies, the Sensory scale typically appears to have the lowest validity. This fits with other conceptualizations of Autism; for example, even the Diagnostic and Statistical Manual of Mental Disorders (4th ed.) does not specifically include sensory deficits as diagnostic criteria for autism . This provides further evidence for the use of the ABC as a screening tool rather than a strict diagnostic measure. Clinicians should exercise caution when using individual scales of the ABC to screen for autism and instead should utilize the entire checklist and its total raw score . In addition, the ABC has not been shown to distinguish autism from other cases of developmental disorders as well as some other autism screening measures, such as the Childhood Autism Rating Scales (CARS) . Overall, the ABC has a concurrent validity coefficient of 0.67 with the CARS . The ABC shows a concurrent validity coefficient of 0.80 with the Pervasive Developmental Disorders Rating Scale (PDDRS) [2, 3].
The ABC total raw score has shown adequate reliability for screening purposes, though the scales individually have shown less reliability. Test–retest reliability reported by the authors is 0.87, but few other studies have examined test–retest reliability with the ABC. Measures of interrater reliability have also shown mixed results. It should be noted that many of the studies which show low interrater reliability tend to compare parent and teacher ratings. In these studies, parents tend to have higher total scores than teachers. It is possible, however, that the different environments seen between the home and school could account for some this variability. Clinicians should carefully consider the lack of strong interrater reliability evidence when comparing scores obtained by parents and teachers on the ABC.