Investigating the Receptive-Expressive Vocabulary Profile in Children with Idiopathic ASD and Comorbid ASD and Fragile X Syndrome.
Eileen Haebig, Audra Sterling
PMID 27796729WHAT IT FOUND
A meaningful relative weakness in understanding words was not more common in boys with idiopathic ASD than boys with fragile X and ASD, but boys with idiopathic ASD had larger average gaps between understanding and spoken words.
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Key findings
01Boys with idiopathic ASD had larger average discrepancies between receptive and expressive vocabulary growth scores than boys with ASD + FXS, and this remained after nonverbal IQ was included.
02Of the 22 boys with idiopathic ASD, 8 had significantly lower receptive than expressive standard scores; of the 28 boys with ASD + FXS, 4 did, and the group difference was p = .099.
03Nonverbal IQ and expressive vocabulary were positively associated with receptive vocabulary, while receptive vocabulary predicted expressive vocabulary and nonverbal IQ did not significantly predict expressive vocabulary (p = .088).
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What it does not show
The study included only 50 boys, so it had limited power to detect group differences or predictors. The groups differed in nonverbal IQ, with the idiopathic ASD group having higher scores, which complicates comparison. The children were only school-age and adolescent boys, so results do not cover younger children or girls. The receptive and expressive vocabulary tests place different demands on children, and the receptive test may be less sensitive to vocabulary deficits. ASD plus fragile X syndrome was classified using ADOS cut-off scores, and no fragile X-only comparison group was included. The study measured children once, so it cannot explain why receptive-expressive differences occur.
Declared interests
One author reported F31 DC013485 support for this work, and another reported a research grant from R03 DC011616 that supported the study. The authors reported no other conflict of interest.
The easy way to misread this
Do not conclude that boys with ASD and fragile X syndrome usually have a receptive vocabulary weakness. The group difference in meaningful receptive weaknesses did not reach significance (p = .099), and most boys in both groups did not show it.