Sex Differences in Item Specific Analyses of ADI-R in Preschool-Aged Boys and Girls with ASD

Background: Females are diagnosed with autism spectrum disorder (ASD) at a ratio of one for every four males and are often diagnosed at a later age. Evaluating sex differences in the behavioral profiles of children with ASD at the time of diagnosis may provide insight into why females are often diagnosed at a later age.

Objectives: Females in this cohort had a significantly higher ADI-R social communication algorithm score than males (p = 0.0177). We carried out item specific analyses in reciprocal social interactions (RSI), communication, and restrictive, repetitive, and stereotypical (RRS) behaviors measured on the ADI-R to further investigate this difference. As a secondary analysis, we conducted a median split of males and females by age of diagnosis to compare symptoms in younger versus older males and females.

Methods: Participants include 100 preschool-aged children with ASD (mean age 36.13 months). 50 females (age of diagnosis range 13-41 months; DQ range 29-112; ADOS composite score range 4-10) were matched to 50 males (age of diagnosis range 14-45 months; DQ range 29-113; ADOS composite score range 4-10). The ADI-R, an assessment that evaluates current and previous symptoms of ASD and aids in diagnosis, was administered to parents. To evaluate the effect of age at diagnosis on symptom severity, males and females were divided at the median to define those diagnosed at a younger age (< 30 months) versus a later age (> =30 months). Analysis of variance was used to investigate differences between males and females with ASD and males and females diagnosed at younger versus older ages for each item on the ADI-R algorithm.

Results: There were significant sex main effects in the RSI and communication sections. Within RSI, females were more affected in their failure to use nonverbal behavior to regulate social interaction (p = 0.0070), range of facial expressions used to communicate (p = 0.0071), seeking to share enjoyment with others (p = 0.0014) and quality of social overtures (p = 0.0430). In the communication section, females showed increased impairment in their lack of, or delay in, spoken language and failure to compensate through gesture (p = 0.0203) and in pointing to express interest (p = 0.0437). When evaluating groups split by age, we found these differences were most pronounced in the younger females with ASD relative to females diagnosed at an older age and males of all ages. No significant differences between males and females were observed in any items related to RRS patterns of behavior.

Conclusions: Females diagnosed at a younger age exhibited higher parent-perceived levels of impairment in specific aspects of reciprocal social behavior and communication, suggesting that younger females may need to exhibit greater perceived-impairment for parents to seek a clinical diagnosis. These differences in severity are seen only in the social and communication categories of the ADI-R. In contrast to recent reports showing less severe RRS patterns of behaviors in females with ASD, we did not observe any differences across males and females as measured by the ADI-R.