The Relationship Between Single-Word Speech Severity and Intelligibility in Childhood Apraxia of Speech

Purpose: The purpose of this study was to investigate the association between perceived single-word speech severity and intelligibility in children with childhood apraxia of speech (CAS), with and without comorbid language impairment (LI), and to investigate the contribution of different CAS signs to perceived single-word speech severity and single-word intelligibility. Method: Thirty children with CAS, 18 with comorbid LI, completed the Goldman-Fristoe Test of Articulation-Second Edition (GFTA-2). Trained judges coded children's responses for signs of CAS and percent phonemes correct. Nine listeners, blind to diagnoses, rated speech severity using a visual analog scale. Intelligibility was assessed by comparing listeners' orthographic transcriptions of children's responses to target responses. Results: Measures of speech severity (GFTA-2 standard score, number of unique CAS signs, total CAS signs, and mean severity rating) were significantly correlated with measures of intelligibility (GFTA-2 raw score, percent phonemes correct, and mean intelligibility score). Speech severity and intelligibility did not differ significantly between children with and without LI. Only consonant errors contributed significant variability to speech severity. Consonant errors and stress errors contributed significant variability to intelligibility. Conclusions: Findings suggest that visual analog scale ratings are a valid and convenient measure of single-word speech severity and that GFTA-2 raw score is an equally convenient measure of single-word intelligibility. The result that consonant errors were by far the major contributor to single-word speech severity and intelligibility in children with CAS, with stress errors also making a small contribution to intelligibility, suggests that consonant accuracy and appropriate lexical stress should be prime therapeutic targets for these children in the context of treatment addressing motor planning/programming, self-monitoring, and self-correcting.