CHARACTERISING MULTIDIMENSIONAL COMMUNICATION IMPAIRMENT IN AUTISM SPECTRUM DISORDER USING ITEM-LEVEL ADI-R MODELLING

Communication impairment is a core feature of autism spectrum disorder (ASD), yet its underlying structure and phenotypic organisation remain poorly defined. Marked heterogeneity exists in both the severity and pattern of communicative difficulties and reliance on total or subscale scores may obscure meaningful domain-specific variation. This study aimed to characterise latent dimensions and phenotypes of communication impairment in ASD using item-level data from the Autism Diagnostic Interview-Revised (ADI-R). Communication subscale data from 3,957 individuals in the Autism Genetic Resource Exchange (AGRE) dataset were analysed using an integrated variable and person-centred framework. Distributional assessment indicated non-normal, ordinal item properties, supporting the use of latent class modelling alongside variable-centred analysis. Exploratory factor analysis (EFA) identified a four-factor structure capturing social play and gesture use, non-verbal communication, conversational and pragmatic language and atypical language features, which was supported by confirmatory factor analysis. Latent class analysis identified six distinct communication phenotypes characterised by heterogeneity in both overall severity and domain-specific profiles of impairment. Integration analyses revealed systematic differences in expression of the EFA-derived communication factors across classes. Validation using the ADI-R social interaction domain score, which was not included in class construction, demonstrated significant between-class differences, supporting construct validity. Together, these findings highlight the multidimensional and heterogenous nature of communication impairment in ASD. By refining behavioural phenotypes through item-level modelling, this work provides a framework for more precise stratification of individuals, with potential to improve investigations of genetic architecture underlying communication variation in ASD.