A Comparison of Aberrant Behavior Checklist (ABC) Factor Scores in Children with Autism Spectrum Disorder (ASD) and Prader Willi Syndrome (PWS)

Background:  Autism Spectrum Disorder (ASD) is frequently diagnosed in association with Prader Willi Syndrome (PWS), a genetic disorder that results from lack of paternally derived imprinted material on chromosome 15q11-q13 (a region also implicated in the etiology of ASD). Previous studies have noted, however, that there are differences in the way that restricted and repetitive behaviors are displayed in children with ASD and PWS. To date, no research has investigated the potential differences/similarities in social impairments or associated symptoms (e.g., irritability or hyperactivity) between children with ASD and PWS.

Objectives:  To compare the Aberrant Behavior Checklist (ABC) Factor Scores of (1) Lethargy/Social Withdrawal; (2) Stereotypic Behavior; (3) Inappropriate Speech; (4) Irritability; and (5) Hyperactivity/Non-compliance between children with ASD and PWS.

Methods:  Children with ASD and PWS, ages 5-17, were enrolled in two separate studies. Children with ASD (n=23) participated in a randomized double-blind crossover study to evaluate the safety and efficacy of Trichuris Suis Ova (TSO), and children with PWS (n=20) participated in an 8 week double-blind treatment study of intranasal OXT (IN-OXT) vs. placebo. The ABC, a 58-item informant-based rating scale, was completed by parents during the baseline visit of both studies.

Results:  There were no significant differences between children with ASD and PWS in terms of gender, race, or age. There were, however, significant baseline performance differences on the Stanford Binet-5 Abbreviated IQ (SB-5 ABIQ); children with ASD scored higher than children with PWS (t=2.204, df=41, p=0.033). The SB-5 ABIQ was therefore used as a co-variate in the analyses of the ABC Factor scores. After controlling for baseline ABIQ, children with ASD had significantly higher scores (i.e., more symptomatology) on the ABC Stereotypic Behavior Factor and the ABC Hyperactivity/Non-compliance Factor compared to children with PWS (F=33.235, p<0.001 and F=23.694, p<0.001, respectively). Differences on the ABC Irritability and Social Withdrawal/Lethargy Factors approached significance (F=3.83, p=0.057 and F=3.75, p=0.06, respectively), with ASD children again having elevated scores. No difference between the groups was found on the Inappropriate Speech Factor.

Conclusions:  Compared to children with PWS, children with ASD were rated by their caregiver as having greater symptomatology across all but one of the ABC Factors. More specifically, children with ASD had significantly higher scores on the ABC Stereotypic Behavior and Hyperactivity/Non-compliance Factors. Elevated scores for children with ASD on the ABC Irritability and Lethargy/Social Withdrawal Factors approached significance compared to children with PWS. These findings were not due differences in baseline intelligence. Future studies should look at item differences within each ABC Factor, in terms of frequency and severity, to more explicitly differentiate their behavioral manifestations in children with ASD and PWS.