Gender Differences on the Newly Proposed ADOS-2, Module 4 Algorithm in ASD without ID: A Multi-Site Study

Background: There has been increased interest in possible differences in symptomatology in females with ASD without ID as compared to males (Van Wijngaarden-Cremers et al., 2014). Traditionally, females with ID were thought to be more severely affected than males. Current research questions whether this is a true discrepancy or a methodological manifestation of mis- or under-diagnosis in females with ASD without ID (Halladay et al., 2015). The algorithm for the ADOS Module 4, appropriate for verbally fluent adolescents and adults, has been recently updated (Hus & Lord, 2014), though gender differences in the algorithm and items have not yet been explored.  

Objectives: The purpose of this study was to investigate gender differences in core symptoms of ASD on gold-standard diagnostic measures via parent interview, parent report, and clinician observation. 

Methods:  

Participants included 255 individuals (n=53 females) across four research-reliable sites with a confirmed ASD diagnosis, ages 11-61 years, with either a full-scale (M=107.23, SD=17.71) or verbal (M=109.14, SD=17.93) IQ>70. There were no significant gender differences in age or full-scale or verbal IQ. All participants were assessed using Module 4 the Autism Diagnostic Observation Schedule (ADOS; Lord, Rutter, DiLavore, & Risi, 2002) or its recent revision the ADOS-2 (Lord et al., 2012). A subsample received the Autism Diagnostic Interview-Revised (ADI-R; Rutter, Le Couteur, & Lord, 2003) (n=33 females, n=157 males) and the Social Responsiveness Scale (SRS/SRS-2; Constantino & Gruber, 2004; Constantino & Gruber, 2012) (n=33 females, n=144 males). 

Results:  

There were no significant gender differences on any ADI-R subscales, but females scored significantly higher than males on the SRS total score (t= -2. 39, p<.01). On the ADOS, there was a trend towards males being rated as more impaired on the updated algorithm (t= 1.92, p=.06). Chi-square analyses were used to examine differences on individual items on the ADOS. Ratings of “3” were converted to “2” and ratings of “7/8” were converted to “0.” Males were rated as significantly more impaired on the following items: “Stereotyped/Idiosyncratic Use of Words of Phrases” (χ²=9.37, p<.01), “Descriptive, Conventional, Instrumental or Informational Gestures” (χ²=7.12, p<.05), “Communication of Own Affect” (χ²=8.51, p<.01), and “Empathy” (χ²=9.40, p<.01).

Conclusions:  

Historical parent report of ASD symptoms via the ADI-R did not reveal gender differences in the present sample. However, parents rated concurrent ASD symptoms on the SRS as more impaired in females than males. Males and females performed similarly on the majority of ADOS items though males were rated as having more severe ASD symptoms in several social communication skills, including two items on the newly proposed ADOS algorithm. Findings from this study indicate that although females look the same as (or better than) males on a few key symptoms on gold standard diagnostic measures, parents observe more social problems in the real world. This may be due to our societal expectations of greater social skills from cognitively able females or because our diagnostic tools are built for and standardized on a majority male population and may not adequately capture ASD in females.