Restricted Interests and Repetitive Behaviors Behavior As a Distinguishing Feature of Autism Spectrum Disorder (ASD) in Nonverbal Children

Background:  

Differentiating ASD from other developmental disorders can be particularly difficult among nonverbal patients (NV).

Objectives:

To explore diagnostic accuracy and autism symptom profiles of nonverbal children with ASD (ASD-NV) in a large autism registry.

Methods:

Fifty-five ASD-NV children ages 6-17 years were recruited from a large, voluntary ASD registry. Participants had a confirmatory score >=12 on the Social Communication Questionnaire (SCQ)-Lifetime. Nonverbal status was determined by a “no” response to the SCQ-Lifetime question: “Is she/he now able to talk using short phrases or sentences?” Participation was limited to one of four US geographic regions so participants could receive an in-person ASD assessment and cognitive testing. Parents completed online questionnaires -- Social Responsiveness Scale (SRS); Adaptive Behavior Assessment System-Second Edition (ABAS-II); Repetitive Behavior Scale, Revised (RBS-R) -- and produced evidence their child had received a community ASD diagnosis. Parents asked a teacher to complete an SRS on their child. Data were compared via ANOVA and post-hoc tests with ratings of 108 verbal ASD (ASD-V) children enrolled in a university-based ASD research program at one of the sites. ASD-V children were split into higher-functioning (ASD-V-HighSoc; n = 75) and lower-functioning (ASD-V-LowSoc; n = 33) based on Vineland-II Adaptive Behavior Scale Socialization Domain score of >=70 and <70, respectively.

Results:  

All 55 ASD-NV children were judged by clinicians to meet criteria for ASD (CI₉₅: 0.935-1.00), and all met ASD cut-offs on both the ADI-R and the ADOS. All exhibited low adaptive functioning at the floor of the ABAS-II, and cognitive functioning was either untestable or at the floor of the selected test(s).

RBS-R: The RBS-R was scored according to the Lam/Aman five-factor solution and scores compared across the three groups controlling for age and sex. There were no statistically significant differences across the three groups for “Ritualistic/Sameness Behavior” and “Restricted Interests.”  There were no statistically significant differences across ASD-NV and ASD-V-LowSoc for “Self-Injurious Behavior” and “Compulsive Behavior”; however, both lower-functioning groups more prone to such behaviors than the ASD-V-HighSoc group [F(4,156)=7.086, p<.000 and F(4,156)=4.392, p<.002, respectively]. “Stereotypic Behavior” presented a unique pattern whereby there were statistically significant differences between each group [F(4,156)=21.205, p<.000], with increased presentation of stereotypies corresponding with lower functioning [ASD-NV=11.8(4.88) >ASD-V-LowSoc=7.3(5.12)>ASD-V-HighSoc=5.2(3.99)].

Composite indices of Restricted Interests and Repetitive Behavior (RRB): There were no statistically significant differences across groups for ADI-R Repetitive Behavior. SRS-Teacher Report RRB T-Scores (higher is more severe) were inversely related to level of functioning [F(3, 132)=24.810, p<.000; ASD-NV=90.1.8(12.25) >ASD-V-LowSoc=81.6(17.08)>ASD-V-HighSoc=71.4(12.79)]. SRS-Parent Report RRB T-Scores were comparable for ASD-NV and ASD-V-LowSoc, and both higher than ASD-V-HighSoc [F(3, 157)=11.242, p<.000; ASD-NV=84.2 (10.6) <>ASD-V-LowSoc=87.1 (10.47)>ASD-V-HighSoc=76.8 (11.29)].

See Table 1.

Conclusions:  

ASD-NV children with community diagnoses of ASD met formal diagnostic criteria for ASD and share Restricted Interests/Repetitive Behavior characteristics with ASD-V children, with severity of such characteristics – both composite and at the factor-level – either comparable or greater than those of ASD-V children. Further research may be valuable in determining whether such Restricted Interests/Repetitive Behavior characteristics may be useful in distinguishing ASD-NV children from NV children with other development disorders.