Reliability of Perceptual Measurement of Apraxia of Speech Characteristics

Background: Diagnostic accuracy and reliability of acquired apraxia of speech (AOS) in the presence of co-occurring aphasia and/or dysarthria are crucial for appropriate treatment selection and clinical decision making. However, overlapping symptomology and lack of operationalization of AOS assessment methods have contributed to inadequate interrater reliability of perceptual measures differentially diagnostic of AOS. Purpose: This study investigated factors influencing the operationalization of AOS assessment methods, primarily interrater reliability of perceptual characteristics of differentially diagnostic (i.e., phonetic and prosodic errors) measures in order to inform assessment methods in AOS with concomitant aphasia. Method: Forty participants presenting with varying aphasia subtypes and severities and potential motor speech impairment were included. Speech production errors were analyzed by four raters using narrow transcription methods in response to the spoken language subtest stimuli (Naming, Repetition, and Spontaneous Speech subtests) of the Western Aphasia Battery–Revised (WAB-R). Interrater reliability of perceptual measurement of both differentially diagnostic and nondiscriminatory features of AOS were examined when using consistent stimuli (WAB-R), measures (Apraxia of Speech Rating Scale), and trained raters using narrow transcription methods. Results: Both differentially diagnostic as well as nondiscriminatory speech characteristics were shown to demonstrate adequate ( Cicchetti, 1994 ) interrater reliability across a variety of aphasia subtypes and severities in people with and without a diagnosis of AOS. Conclusions: The current work provides preliminary evidence of adequate interrater reliability of perceptual features of AOS using consistent stimuli (WAB-R spoken language stimuli), measures (Apraxia of Speech Rating Scale), and trained raters using narrow transcription. These preliminary results support the consistency and operationalization of assessment methods through the investigation of reliability of perceptual measurements of differentially diagnostic characteristics of AOS in the presence of aphasia.