17478
Does ASD Severity Predict Minimally Verbal Outcome By School Age?
A significant minority of children with autism spectrum disorder (ASD) are considered “minimally verbal,” characterized by lack of expressive language beyond single words. Although language outcomes have been well-studied, limitations of measures have prevented observationally-based ratings of ASD severity to be explored with respect to the relationship between ASD severity and language through the preschool years.
Objectives:
The goals of this study were to measure expressive language across approximately 2 years in preschool-aged children, and evaluate predictors of language level at age 5 years.
Methods:
Participants were children with DSM-IV diagnosed autistic disorder (n=70) drawn from a larger longitudinal study. Additional inclusion criteria were (a) two study visits at least 11 months apart, and (b) follow-up evaluation between 4 years, 6 months and 6 years, 0 months (inclusive). Study measures included the Autism Diagnostic Observation Schedule (ADOS), used in this study to measure overall level of language (item A1), as well as core deficits of ASD (total and domain severity scores), the Autism Diagnostic Interview-Revised (ADI-R), and the Mullen Scales of Early Learning (used to estimate developmental quotient, DQ). Children were classified as “minimally verbal” if they had no words or some single words based on observation from the ADOS; “verbal” children displayed phrase speech.
Results:
The average age at initial evaluation (Visit 1) was 3.56±0.85 years (range 1.76-4.98); the average time to follow up was 1.90±0.81 years (age range at follow up: 4.62-5.98; mean age: 5.45±0.37). Based on the ADOS item A1, 67% (n=47) of the sample was minimally verbal at Time 1. This group did not differ in age from the verbal group. At Time 2, 36% (n=17 of 47) of those who were minimally verbal at Time 1 had developed phrase speech. The remainder of analyses focused on the Time 1 minimally verbal subgroup (n=47). Age at Time 1 and time-to-follow-up were not related to minimally verbal status at Time 2 and were therefore excluded from further analyses of predictors. In a logistic regression, Time 1 NVDQ was significantly related to Time 2 minimally verbal status, such that each point of NVDQ at Time 1 conferred a 5% increase in the odds of being verbal at Time 2 (OR = 0.95, p<.049). Time 1 VDQ was not significantly associated with Time 2 verbal status (OR=.97, p=.15). ADOS domain calibrated severity scores (Social Affect and Restricted/Repetitive Behavior) did not significantly predict minimally verbal status, with or without NVDQ in the equation.
Conclusions:
The results of this study suggest that although there is growth in expressive language over time through the end of the preschool period, many children with ASD remain minimally verbal entering school age. Consistent with previous findings, NVDQ is a significant predictor of who will develop phrase speech by age 5. ADOS domain calibrated severity scores were not associated with language development, indicating that neither severity of social affect, nor severity of restricted and repetitive behaviors heavily influenced the development of expressive language development during the preschool years.