Same or Different: The Overlap Between Children With Auditory Processing Disorders and Children With Other Developmental Disorders: A Systematic Review

Abstract

Objectives: Children diagnosed with auditory processing disorders (APD) experience difficulties in auditory functioning and with memory, attention, language, and reading tasks. However, it is not clear whether the behavioral characteristics of these children are distinctive from the behavioral characteristics of children diagnosed with a different developmental disorder, such as specific language impairment (SLI), dyslexia, attention-deficit hyperactivity disorder (ADHD), learning disorder (LD), or autism spectrum disorder. This study describes the performance of children diagnosed with APD, SLI, dyslexia, ADHD, and LD to different outcome measurements. The aim of this study was to determine (1) which characteristics of APD overlap with the characteristics of children with SLI, dyslexia, ADHD, LD, or autism spectrum disorder; and (2) if there are characteristics that distinguish children diagnosed with APD from children diagnosed with other developmental disorders.

Design: A systematic review. Six electronic databases (Pubmed, CINAHL, Eric, PsychINFO, Communication & Mass Media Complete, and EMBASE) were searched to find peer-reviewed studies from 1954 to May 2015. The authors included studies reporting behaviors and performance of children with (suspected) APD and children diagnosed with a different developmental disorder (SLI, Dyslexia, ADHD, and LD). Two researchers identified and screened the studies independently. Methodological quality of the included studies was assessed with the American Speech-Language-Hearing Association's levels-of-evidence scheme.

Results: In total, 13 studies of which the methodological quality was moderate were included in this systematic review. In five studies, the performance of children diagnosed with APD was compared with the performance of children diagnosed with SLI: in two with children diagnosed with dyslexia, one with children diagnosed with ADHD, and in another one with children diagnosed with LD. Ten of the studies included children who met the criteria for more than one diagnosis. In four studies, there was a comparison made between the performances of children with comorbid disorders. There were no studies found in which the performance of children diagnosed with APD was compared with the performance of children diagnosed with autism spectrum disorder. Children diagnosed with APD broadly share the same characteristics as children diagnosed with other developmental disorders, with only minor differences between them. Differences were determined with the auditory and visual Duration Pattern Test, the Children's Auditory Processing Performance Scale questionnaire, and the subtests of the Listening in Spatialized Noise-Sentences test, in which noise is spatially separated from target sentences. However, these differences are not consistent between studies and are not found in comparison to all groups of children with other developmental disorders.

Conclusions: Children diagnosed with APD perform equally to children diagnosed with SLI, dyslexia, ADHD, and LD on tests of intelligence, memory or attention, and language tests. Only small differences between groups were found for sensory and perceptual functioning tasks (auditory and visual). In addition, children diagnosed with dyslexia performed poorer in reading tasks compared with children diagnosed with APD. The result is possibly confounded by poor quality of the research studies and the low quality of the used outcome measures. More research with higher scientific rigor is required to better understand the differences and similarities in children with various neurodevelopmental disorders.

Fig. 1.

Process for identification of included studies. APD, auditory processing disorder. From PLoS Med. 2009;6:e1000097.

Fig. 2.

Venn diagram of the comparisons made in this systematic review and the overlap and differences between groups on the outcome of various tests used in the included studies. The performance of children diagnosed with APD on various tests is compared with the performance of children diagnosed with SLI, dyslexia, ADHD, and LD. N identifies the number of studies included. The area of the circles is equal to the number of subjects included in the studies (n). The bold and the outlined numbers show the overlap (no significant differences) on the oucome of the used measurement instruments. Italic numbers illustrate the significant differences between children diagnosed with APD and children diagnosed with other disorders. The encircled italic numbers show the number of measurement instruments (test and subtest level) whereupon children diagnosed with APD perform significantly poorer in comparison with children diagnosed with other developmental disorders. The studies in which children with comorbid disorders (N = 4) were enrolled are not captured in this figure. ADHD, attention-deficit hyperactivity disorder; APD, auditory processing disorder; CHAPPS, Children’s Auditory Processing Performance Scale (Smoski et al. 1998); DPT, Duration Pattern test; LD, learning disorder; LiSN-S, Listening in Spatialized Noise test-Sentence (Cameron & Dillon 2007, 2008); SLI, specific language impairment; SRT, speech reception threshold.