VIQ = PIQ in children with PDD-NOS

Background: Previous studies in children with autism often show a PIQ > VIQ pattern in children with autism and a VIQ > PIQ pattern in children with Asperger Syndrome. For the milder form of the ASD's, PDD-NOS (which occurs much more frequently), intelligence profiles are unknown. We often presume children with PDD-NOS will show a similar intelligence profile to children with autism. For treatment and prognosis purposes it is important to be aware of possible strenghts and weaknesses in the cognitive profile of these children.

Objectives: Therefore the aim of this study was to compare IQ scores of children with PDD-NOS to those of children with autism and to those of children with Asperger syndrome. A second aim of this study was to assess strenghts and weaknesses in IQ profiles of children with PDD-NOS.

Methods: The WISC was administered to 100 children, aged 6-12 years, with PDD-NOS (n = 76), autism (n = 13) and Asperger syndrome (n = 11).

Results: IQ scores did not differ between the three groups. In children with PDD-NOS, all IQ scores were in the average range, their VIQ = PIQ and their FFD factor was lower than the other Kaufman factors.

Conclusions: The typical autism PIQ > VIQ pattern was not found in children with PDD-NOS. These children have IQ scores in the average range and show a weakness on subtests that measure attention and concentration. IQ scores alone are not sufficient to distinguish between PDD-NOS, autism, and Asperger syndrome.