Appropriateness of Standardized Testing to Determine Behavioral Treatment Eligibility of Children with ASD

Background: Frequently, behavioral intervention programs for children with ASD are faced with the question of which children to admit for treatment because of limited resources. Some programs require standardized assessments of cognitive, language, and/or adaptive behavior functioning in order to make intake decisions; children who are “untestable” on one or more such measures may not be admitted for treatment. Thus, it is important to know whether or not “testability” at baseline is a valid measure of a child's potential response to treatment. A measure used in many assessment batteries is the Peabody Picture Vocabulary Test-III (PPVT-III), which requires a child to point to one of four pictures on a page in response to a spoken word cue.

Objectives: The primary goal of this exploratory study was to examine changes in children's testability on the PPVT-III over three time points, starting with assessment prior to the initiation of early intervention (T1). A secondary goal was to determine whether there were differences on measures of aberrant behavior, adaptive behavior, and autism severity over time between children who were and were not testable on the PPVT-III at T1.

Methods: Sixty-nine children with ASD (84% males) were assessed at T1 (mean CA=50 months) and both 6 months (T2) and 12 months (T3) thereafter. Single word receptive vocabulary was measured with the PPVT-III. The sample was divided into children who were unable to complete the PPVT-III at T1 and those who attained a raw score score ≥1. Independent t-tests were used to examine whether there were differences between the two groups on subscales of the Temperament and Aberrant Behavior Scale (TABS), Vineland Adaptive Behavior Scale adaptive behavior composite (VABS ABC), and/or Childhood Autism Rating Scale (CARS).

Results: At T1, 51% of children (n=35) were untestable on the PPVT. There were significant differences (p<.001) between the testable and untestable groups on the TABS detached and under-reactive behavior subscales, CARS, and VABS ABC, with the untestable group showing more evidence of aberrant behavior, higher autism severity, and lower adaptive behavior. At T2, 29% of the children were untestable on the PPVT-III, a decrease of 22%. Again, significant differences were found between the two groups that were identical to T1. At T3, 25% of the children were untestable on the PPVT-III, a decrease of only 3%. The pattern of between-group differences identified at T1 continued to be evident.

Conclusions: The results indicate that a significant number of children who could not point to pictures on demand at T1 were able to do so after 6 months of behavioral intervention. The children who continued to be untestable at all time points presented with more detached and under-reactive behavior, higher autism severity, and lower adaptive behavior scores. It appears that the persistently untestable children were those who might be expected to make the least progress in behavioral intervention over time. The results suggest that a 6-month trial of behavioral intervention would be appropriate prior to determining which children are likely to benefit from this form of treatment.