Gender Differences in CSBS Scores

Background:  The prevalence of autism is reported to be higher among males than females, although the exact mechanism underlying this gender difference is unknown. Evidence suggests that phenotypic gender differences may account for some of this male bias in prevalence (Gould & Ashton-Smith, 2011). Specifically, differences in the manifestation of symptoms (e.g. females exhibiting fewer stereotypies) may result in females being underdiagnosed (Werling & Geschwind, 2013). The implications of gender differences in phenotypic presentation are diverse, starting with a need to re-examine, and potentially amend screening and diagnostic tools.

Objectives:  This study’s objective was to assess if gender differences exist in screening and diagnostic methods for autism. Specifically, we examined if Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist (CSBS) scores varied between male and female toddlers. The CSBS is a broadband screening tool used to detect various disorders, including autism (Wetherby et al., 2008). The CSBS comprises three composite scores (social, speech, and symbolic) and a total score.

Methods:  Data were collected as part of a larger study, in collaboration with UCSD, that is testing a model called Get S.E.T. Early (S=Screen, E=Evaluate, T=Treat), designed to detect, evaluate, and treat autism within the first 2 years of life. Children from the general Phoenix and San Diego population are screened using the CSBS at 12-, 18-, and 24-month well-baby checkups. Children who fail the CSBS are referred for free developmental evaluations. Analyses for this study focused on two groups of children from the Phoenix cohort: (1) 7504 toddlers (3874 females and 3630 males) who passed all sections of the CSBS, and (2) 324 toddlers (82 females and 242 males) who failed at least one section of the CSBS and who received a developmental evaluation. Mean scores for males and females were compared using Bonferroni-corrected Mann-Whitney U tests.

Results:  For toddlers who passed the CSBS, females scored significantly higher than males for the social (MD=0.36, r=.07), speech (MD=0.41, r=.09), and symbolic (MD=0.40, r=.07) composites, and for the total score (MD=1.17, r=.08). For toddlers who failed the CSBS and who received a developmental evaluation, no significant differences between males and females emerged for any composite score or the total score. Approximately 56% of the 242 evaluated males were at-risk for ASD, while only 38% of the 82 evaluated females were at-risk for ASD.

Conclusions:  Although females who passed the CSBS had significantly higher composite scores, and total scores, than males who passed the CSBS, mean differences were negligible with small effect sizes, and statistical significance was likely achieved as a result of the large sample size. No gender differences emerged for children who failed the CSBS and who received a developmental evaluation. Despite this, approximately 3 times as many males than females failed the CSBS and received a developmental evaluation, and among those who received the developmental evaluation the odds of being at-risk for ASD were 2 times higher for males than females. This suggests that increased sensitivity on screening and diagnostic assessments for ASD is needed to better reflect the autism phenotype expressed by females.