Assessing Gender Differences in Autism Spectrum Disorder Using the Gendered Autism Behavioral Scale (GABS)
Objectives: To assess the inter-rater reliability of the GABS, and replicate pilot findings that the GABS differentiates phenotypic expression of females versus males from video-recorded Module 3 and 4 ADOS-2 administrations.
Methods: A UCL researcher involved in piloting the GABS trained a RI-CART researcher to code the GABS. The first RI-CART researcher then trained a second, independent RI-CART researcher. During this second training, instances in which the RI-CART researchers could not reach consensus on a given item were resolved by the UCL researcher.
This study analyzed recorded ADOS-2 assessments from males (n = 40) and females (n = 20) aged 4-59 years enrolled in RI-CART, a state-wide, community-based sample. Participants had community diagnoses of ASD and a positive ADOS-2. Female participants were matched with two male participants of similar age, IQ, and/or Vineland ABC scores.
Results: Acceptable inter-rater reliability was achieved between the UCL and first RI-CART researcher (k = 0.69) as well as the first and second RI-CART researchers (k = 0.72). Chi-squares indicated male participants received significantly higher scores than female participants on GABS items C2 (externalising difficulties) X2 (1, n = 60) = 6.56, p = .010 and D1 (reported interests frequency/intensity) X2 (3, n = 60) = 8.81, p = .032, indicating male participants reported more externalizing symptoms and more intense restricted interests than female participants. However, the difference in overall GABS scores between males (M = 14.52, SD = 5.42) and females (M= 16.38, SD= 5.05) was not significant t(58)= 0.784, p = .076.
Conclusions: This study found acceptable inter-rater reliability between GABS assessors across UCL and RI-CART. Validity tests resulted in a partial replication of female vs. male differences on the GABS. This lack of differences may be attributable to an overly small and/or heterogeneous sample. The GABS could provide a means of extracting valuable data on the hypothesized female autism phenotype through a widely employed assessment, the ADOS-2. Future research should assess the GABS’ reliability and validity in larger samples, and consider additional tests of validity such as differentiating females with ASD and a negative ADOS-2 (i.e., false negatives) from females with concordant ADOS-2 and clinical diagnosis.