Does the Verbal Comprehension Index (VCI) Score of the WISC-IV:UK Detect Language Impairments in School-Aged Children with Autism Spectrum Conditions?

Background: Language impairment is a core feature of autism spectrum conditions (ASC).  It can range from a difficulty understanding or using single words and short sentences to more subtle, higher level language difficulties.  The Wechsler Intelligence Scale for Children® — Fourth Edition (WISC-IV^UK) is one of the most widely used cognitive assessments for school-aged children in the United Kingdom.  Its Verbal Comprehension Index (VCI) evaluates particular aspects of linguistic ability, such as verbal concept formation and verbal reasoning.  In clinical practice, general conclusions about the language development of children with ASC are often drawn from the VCI score.  It is sometimes assumed that additional language testing is not indicated once a child’s VCI falls within the average range.

Objectives: To examine the ability of the VCI score of WISC-IV^UK to detect receptive and expressive language impairments in a group of school-aged children with a diagnosed ASC.

Methods: A cognitive assessment (WISC-IV^UK) and language assessment (Clinical Evaluation of Language Fundamentals - Fourth Edition UK; CELF-4^UK) were individually administered to a sample of children (n=26) with a confirmed diagnosis of an ASC who were in their final year at mainstream primary school (Mean age: 11 years; 3 months). A comparison was made of the following composite scores for each participant: the Perceptual Reasoning Index (PRI) and Verbal Comprehension Index (VCI) of WISC-IV^UK; the Receptive Language Index (RLI), Expressive Language Index (ELI) and Language Memory Index (LMI) of CELF-4^UK.

Results: Just under two-thirds of the sample (17 children) performed within the language impairment range (mild, moderate or severe) on at least one of the three CELF-4^UK composites.  However, 8 of these children (or 47% of those with language impairments) performed within the average range (score of 90 or above) on the VCI of WISC-IV^UK. The VCI did not detect linguistic difficulties in almost half of those scoring in the language impairment range on CELF®–4, therefore.  Furthermore, the majority of children (7 out of 8 or 87.5%) in this undetected group had language difficulties in the moderate and/ or severe range (CELF-4^UK).  The VCI proved accurate in detecting linguistic difficulties in children whose assessment profiles were characteristic of a Specific Language Impairment (SLI), however.  Just over a quarter (26.9%) of the sample of 26 children had language profiles which met ICD-10 and DSM-IV criteria for SLI (with the exception of the coexistent ASC diagnosis) and the majority of their VCI scores (6 out of 7 or 85.7%) fell below the average range (i.e. 90 or below).

Conclusions:   Undiagnosed language impairments are known to affect many aspects of the lives of children with ASC, including their psychological wellbeing, social interaction with peers, self-regulation of behaviour and ability to access the educational curriculum.  Clinicians must be wary of drawing conclusions about a child’s language development based solely on the VCI score, since it evaluates only certain aspects of linguistic development.  Our findings highlight the importance of access to a comprehensive multidisciplinary assessment for children with ASC, which includes a standardised language assessment.