Discrepancies between parent-reported and clinician-rated autism severity: roles of sex and age.

Introduction: Assessment of autism spectrum disorder (ASD) relies on both parent-reported questionnaires and clinician-administered observational instruments. Although discrepancies between informants are common, their implications for autism severity evaluation remain unclear. This study examined informant discrepancies across parent-reported and clinician-rated measures, focusing on sex- and age-related effects. Methods: Children and adolescents with ASD and typically developing (TD) controls were assessed using parent-reported measures, including the Social Responsiveness Scale, Second Edition (SRS-2), and the Japanese version of the Autism-Spectrum Quotient (AQ-J). Clinician-rated autism severity was assessed using the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2). Two-way analyses of variance were used to examine the diagnostic and sex-related effects. Hierarchical regression analyses were used to evaluate the associations between parent-reported subscales and ADOS-2 severity within the ASD group. Spearman's rank correlations were used to assess age-related changes in discrepancy scores separately by sex. Results: Parent-reported measures robustly differentiated the ASD and TD groups but showed few sex-related differences. In contrast, the ADOS-2 total score differed significantly by sex within the ASD group, with males exhibiting higher clinician-rated autism severity; however, most domain-level scores were not significant. Hierarchical regression analyses indicated limited associations between parent-reported subscales and clinician-rated severity. Sex remained a consistent predictor of ADOS-2 total scores. Age was negatively associated with SRS-2-ADOS-2 discrepancy scores among females, suggesting reduced parent-clinician discrepancy with increasing age in girls. Conclusion: Parent-reported and clinician-rated measures captured overlapping but distinct aspects of autism-related characteristics. The ADOS-2 total score identified a sex-related difference in clinician-rated severity that was not apparent in parent-reported measures; however, these findings should be interpreted cautiously, given documented limitations of the ADOS-2 in detecting some autistic female presentations. Overall, these findings highlight the complementary contributions of parent-reported and clinician-rated assessments and underscore the importance of considering informant perspectives when interpreting autism-related characteristics across contexts.