2016 Gatlinburg Conference Poster
PS-68
Title: Autism Symptom Severity in Fragile X Syndrome: Effects of ADOS Module
Authors: Cynde Katherine Josol, Emma Charlotte Cooper, Angela Thurman, Andrea McDuffie, Leonard Abbeduto
Introduction: Fragile X syndrome (FXS), which is caused by a mutation in a single gene on the X chromosome, is the leading
inherited cause of intellectual disability. Additionally, individuals with FXS, particularly males, are at a high risk for presenting
with symptoms of autism spectrum disorder (ASD). For example, gaze aversion and repetitive behaviors are commonly
associated with the FXS phenotype. The Autism Diagnostic Observation Scale (ADOS) is one of the gold standard diagnostic tools
used to evaluate the presence of ASD symptomatology. Within this measure, one of four modules is administered based upon
expressive language level. The current version of the ADOS was designed to control for language differences and allow
comparison across modules. Although the ADOS is commonly used to assess ASD symptomatology in FXS, there are no data on
whether the different modules function as intended in FXS or on how language level affects measurement outcomes in FXS.
Such data are needed given recent findings suggesting differences in the developmental mechanisms underlying ASD symptom
severity between individuals with FXS and those with idiopathic ASD. In the present study, we examined: (1) the severity of ASD
symptomatology as a function of ADOS module in FXS and (2) the relationship between severity of ASD symptomatology and
chronological age and the relationship between severity of social affective and restricted and repetitive behavior
symptomatology in FXS.
Methods: Participants were 195 individuals with FXS (170 males, 25 females) ranging in age from 3.85 - 23.15 years (M=12.31
years, SD=4.59). Participants were administered the either the ADOS (n=105) or the ADOS-2 (n=90). For participants who
received the ADOS, the Comparison score was computed (Gotham et al., 2009). In addition, the Social Affect Calibrated Severity
scores and the Restricted and Repetitive Behavior Calibrated Severity scores, (Hus et al., 2014), were computed for all
participants. In the present sample, participants received either a Module 1 (n=23), 2 (n=84), or 3 (n=88).
Results: Results indicated that the overall severity of ASD symptomatology varied significantly as a function of module, with less
severe symptomatology observed for individuals with FXS who received a Module 3 relative to those who received a Module 2.
Moreover, although there was no effect of module on severity of social affective symptomatology, severity of restricted and
repetitive behaviors did vary as a function of module, with more severe scores observed for individuals who received a Module 1
than for those who received a Module 3. Differences were also observed across modules in the association between severity of
social affective and restricted and repetitive behavior symptomatology.
Discussion: It is well documented that there are a number of similarities between the phenotypes associated with FXS and
idiopathic ASD. That being said, there is a growing body of research indicating that the developmental mechanisms underlying
the features shared between these two conditions also may be different in clinically important ways. Given these findings, it is
important to consider the possibility that the tools found to be effective for characterizing symptoms present in individuals with
idiopathic ASD may not translate to individuals with FXS. Our data suggest that, for individuals with FXS, severity of ASD
symptomatology and the association between severity in the two symptom domains differ across the different language level
categories utilized by the ADOS. Clinical and theoretical implications will be discussed.
References/Citations:
• Gotham et al. (2009). Standardizing ADOS scores for a measure of severity in autism spectrum disorders. JADD, 39, 693705.
• Hus et al. (2014). Standardizing ADOS domain scores: Separating severity of social affect and restricted and repetitive
behaviors. JADD, 44, 2400-2412.