PS-22
Title: The Relationship between ADOS and CARS for Males with FXS
Authors: Sarah Nelson, Robyn Tempero Feigles, Joan Gunther, Audra Sterling, Andrea McDuffie, Leonard Abbeduto
Introduction: Many individuals with fragile X syndrome (FXS), the leading inherited cause of intellectual disability, display symptoms of autism spectrum disorder (ASD). Studies examining the behavioral features of FXS, therefore, often include a metric of autism symptom severity or divide their samples into dichotomous groups with and without ASD. Two measures commonly used to characterize autism in samples of individuals with FXS for research purposes are the Autism Diagnostic Observation
Schedule - 2nd Edition (ADOS-2) and the Childhood Autism Rating Scale - 2nd Edition, Standard Version (CARS2-ST). Although the
ADOS is considered a gold standard measure for diagnosing autism, the CARS has been used in a large number of studies of FXS.
Therefore, it is important to understand the ways in which the results of those studies are different from studies that have used the ADOS as a means to represent autism status or symptoms. The goal of the present study was to examine the relationship between the ADOS and the CARS to provide insight into how these instruments represent autism diagnostic status and autism symptom severity.
Research Questions
1.
What is the correspondence between the CARS and ADOS as regards the ASD diagnosis?
2.
What is the correspondence between the CARS and ADOS as regards the severity of ASD symptoms?
3.
How do CARS and ADOS scores vary as a function of child characteristics?
Methods: All ADOS assessments were administered and scored by research-reliable staff according to the ADOS manual. Two trained researchers watched video recordings of ADOS assessments and scored using the CARS2-ST. A third researcher then watched and scored four videos from each researcher's set, comprising 20% of the total sample. Inter-scorer agreement was calculated on an item-by-item basis, and a score within a half-point was considered in agreement. Mean agreement was 90%, with a range of 86-93%.
Results:
Question 1 – Using the diagnostic classifications of autism (0,1) provided by the ADOS and CARS, a Pearson Chi Square revealed there was not a significant degree of concordance between the ADOS and CARS in the number of individuals who were classified as having autism/no autism using these measures: Chi-square = 2.80, p=.094. The nonparametric correlation between the two measures was .32, indicating a small and marginally significant degree of association.
Question 2 – Using the continuous measures of autism symptom severity provided by ADOS severity scores and CARS total scores, we found a moderate and significant correlation between the two measures, r(28) = .58.
Question 3 – There were no significant correlations between ADOS symptom severity and either chronological age, receptive vocabulary, expressive vocabulary, or nonverbal IQ.
Total CARS scores were significantly and negatively correlated with receptive and expressive vocabulary and with nonverbal IQ.
Discussion: Individuals with FXS often display symptoms that warrant an ASD diagnosis. Past studies examining the presence of
ASD symptoms in individuals with FXS have used both the CARS and the ADOS to determine diagnostic status. The results of this study indicate that there is some, albeit limited, correspondence between how the ADOS and CARS diagnostically classify the presence of autism in FXS. There was a stronger correlation between the measures as regards ASD symptom severity. Finally, consistent with the design of the ADOS, severity scores were largely unrelated to measures of child age, language, and cognition.
In contrast, language scores were related to CARS severity scores. These results demonstrate that the scores of the CARS and the
ADOS do not always provide the same diagnostic categories or qualifications of autism symptom severity and that the confounding of language level of ASD severity in the CARS makes it less preferred than the ADOS for assessing individuals with
FXS.