Objectives: The purpose of this study was to determine (1) whether the individuals with SLOS+ASD have distinctive autistic profiles as measured by the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule-G (ADOS-G), (2) whether the individuals with SLOS+ASD have distinctive profiles in terms of IQ and adaptive behavior, and (3) which components of the ADI-R and ADOS-G contribute most to the ASD diagnosis.
Methods: Twenty-three participants (mean age 7.8±3.3 years) with SLOS were assessed by measures of autism features, IQ (Stanford Binet, 4th Edition (SB-IV) or Mullen Scales of Early Learning), and adaptive function [Vineland Adaptive Behavior Scales (VABS)]. We divided the SLOS subjects according to their summary diagnoses from the ADI-R/ADOS-G/DSM-IV and the Non-Verbal Mental Age (NVMA) into 3 groups: SLOS+ASD, NVMA >24 months (n=9), SLOS+ASD, NVMA<24 months (n=7), and SLOS+None, NVMA>24 months (n=7). Descriptive statistics were used for overall assessment of the sample. Characterization of autistic behaviors was performed by non-parametric and regression analyses.
Results: 52% of youths with SLOS met criteria for autism and 70% met criteria for ASD. Cognitive and adaptive profiles of individuals with SLOS+ASD, NVMA<24 months were significantly more impaired than SLOS+ASD, NVMA>24 months and SLOS+None groups. Despite differences in cognition, common patterns emerged among the two SLOS+ASD groups: (1) they both were significantly different from the SLOS+None group on ADOS-G Play/Imagination and (2) they were different at a trend level on Peer Relationships (A4) subdomain of the ADI-R Social. Logistic Regression analyses showed that ADOS-G Play/Imagination (p=0.0019) and A4 of the ADI-R Social (p=0.0005) were the most significant predictors of the ASD diagnosis.
Conclusions: Our findings demonstrate distinct autistic patterns that separated individuals with ASD from the rest of the SLOS cohort. Furthermore, our results indicate that selective impairment in more complex behaviors (i.e., peer relationships) differentiated autism related behaviors in SLOS. Further investigation of this phenomenon in a larger sample and its implications to ASD in general is suggested.