Understanding definitions of minimally verbal across instruments: evidence for subgroups within minimally verbal children and adolescents with autism spectrum disorder

This study determined the prevalence of autism for a defined community, Brick Township, New Jersey, using current diagnostic and epidemiologic methods. The target population was children who were 3 to 10 years of age in 1998, who were residents of Brick Township at any point during that year, and who had an autism spectrum disorder. Autism spectrum disorder was defined as autistic disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS), and Asperger disorder. The study used 4 sources for active case finding: special education records, records from local clinicians providing diagnosis or treatment for developmental or behavioral disabilities, lists of children from community parent groups, and families who volunteered for participation in the study in response to media attention. The autism diagnosis was verified (or ruled out) for 71% of the children through clinical assessment. The assessment included medical and developmental history, physical and neurologic evaluation, assessment of intellectual and behavioral functioning, and administration of the Autism Diagnostic Observation Schedule-Generic. The prevalence of all autism spectrum disorders combined was 6.7 cases per 1000 children. The prevalence for children whose condition met full diagnostic criteria for autistic disorder was 4.0 cases per 1000 children, and the prevalence for PDD-NOS and Asperger disorder was 2.7 cases per 1000 children. Characteristics of children with autism in this study were similar to those in previous studies of autism. The prevalence of autism in Brick Township seems to be higher than that in other studies, particularly studies conducted in the United States, but within the range of a few recent studies in smaller populations that used more thorough case-finding methods.

One of the primary diagnostic criteria for the diagnosis of autism spectrum disorders (ASD) is the presence of a language delay or impairment. Children with ASD are now being identified at significantly younger ages, and prior research has consistently found that early language skills in this population are heterogeneous and an important predictor for later outcome. The goal of this study was to systematically investigate language in toddlers with ASD and to identify early correlates of receptive and expressive language in this population. The study included 164 toddlers with ASD between the ages of 18 and 33 months who were evaluated on several cognitive, language and behavioral measures. Results suggested good agreement among different measures of early language, including direct assessment and parent report measures. Significant concurrent predictors of receptive language included gestures, non-verbal cognitive ability and response to joint attention. For expressive language, the most significant predictors were non-verbal cognitive ability, gestures and imitation. These findings have important implications for intervention programs targeting this population.

Spoken and gestural communication proficiency varies greatly among autistic individuals. Three studies examined the role of oral- and manual-motor skill in predicting autistic children's speech development. Study 1 investigated whether infant and toddler oral- and manual-motor skills predict middle childhood and teenage speech fluency; Study 2 verified those early infant and toddler predictions with historical home video; and Study 3 assessed the relation between autistic children's current-day oral-motor skill and their speech fluency. Infant and toddler oral-motor and manual-motor skills inter-correlated significantly, distinguished autistic children (N = 115) from typically developing children (N = 44), and distinguished autistic children whose current-day speech was minimally fluent (N = 33), moderately fluent (N = 39), and highly fluent (N = 39). These results were corroborated by analysis of historical home video (N = 32) and verified with current-day assessment (N = 40). The prominent associations among early oral- and manual-motor skills and later speech fluency bear implications for understanding communication in autism. For instance, these associations challenge the common assumption (made even in diagnostic criteria) that manual modes of communication are available to autistic individuals - if simply they choose to use them. These associations also highlight a potential confound from manual-motor skills when assessing autistic cognition, receptive language, and 'nonverbal' social communication.