ASD concordance of twins across DSM-IV-TR and DSM-5 diagnostic criteria

Background Previous research has supported a high degree of concordance for ASD among monozygotic twins, but no studies have examined concordance rates using DSM-5 diagnostic criteria for ASD. This pilot study examines monozygotic concordance for ASD from the perspective of both DSM-IV-TR and DSM-5 diagnostic criteria. Method Items of the Autism Diagnostic Interview–Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) were matched to diagnostic criteria (Huerta et al., 2012). Diagnoses were assigned to 14 pairs of monozygotic twins, among whom at least one twin had an autism diagnosis, using DSM-IV-TR and DSM-5 criteria. McNemar tests were performed to determine whether there was a significant difference in sample pairwise concordance rates between the two diagnostic systems. Results Using strict criteria, which required items endorsed from both the ADI-R and the ADOS, eight of the fourteen twin pairs were concordant using DSM-IV-TR criteria compared to five pairs using DSM-5 criteria, yielding pairwise concordance rates of 57.14% and 35.71%, respectively. The use of either the ADI-R or the ADOS (relaxed criteria) resulted in pairwise concordance rates of 85.71% for DSM-IV-TR criteria and 78.57% for DSM-5 criteria. Pairwise concordance rates were not different across DSM-IV-TR and DSM-5 diagnostic criteria using these two methods, but were significantly greater with the use of relaxed as compared to strict criteria for DSM-5. Conclusions In this pilot study, monozygotic pairwise concordance rates were higher for DSM-5 when using information from either the ADI-R or the ADOS, as opposed to both measures.