Objectives: The objectives of this study were (1) to show prediagnostic abnormalities in social and communicative behaviors on home videos of children who later received a diagnosis of one of the pervasive developmental disorders (PDD) and (2) to demonstrate that prediagnostic abnormalities in social and communicative behaviors for children with PDD not otherwise specified will be less prominent than those in children with autistic disorder but still distinguishable from those of typically developing peers.
Study design: Parents of children with PDD each submitted home videos of social events that were made when their child was between the ages of 12 and 30 months, before diagnosis. Two independent observers, unaware of the subjects' diagnoses or purpose of the study, scored the rates of specific anomalies in social and communicative behavior. Two additional observers scored the percentage of time the children were engaged socially or with objects. Data from the experimental group were compared with those of 25 age-matched children with no developmental disabilities.
Results: Significant differences were found between the rates of social engagement and 8 of the 25 specific behaviors of the children in whom PDD was later diagnosed and those of the typical children. The children later given the diagnosis of PDD not otherwise specified had mean frequencies of some social interactions and communicative skills that fell between those of children later given the diagnosis of autistic disorder and those of children with typical development.
Conclusion: In our sample children in whom PDD was later diagnosed could be differentiated from their typically developing peers on the basis of specific anomalies noted in their social and communicative behaviors, especially joint attention. In our sample children with PDD not otherwise specified could have been further differentiated on the basis of the rates of social interaction. Careful assessment of social interaction and communicative behaviors may help to identify children with PDD before the age of 30 months.