Speech Intelligibility Outcomes Associated With Treatment for Acquired Apraxia of Speech: Magnitude of Change and Stability of Measurement

Abstract

Purpose: The purpose of this investigation was to examine single-word speech intelligibility outcomes following sound production treatment in a group of 22 speakers with chronic acquired apraxia of speech (AOS) and aphasia. Also, the stability of repeated posttreatment intelligibility measures was examined for two scoring methods. Method: The Assessment of Intelligibility of Dysarthric Speech was administered twice to each participant at pretreatment and twice at 8 weeks posttreatment. The test–retest reliability of the pretreatment samples was evaluated in a prior study; repeated samples were found to be stable over sampling times. For the current study, the three expert listeners who had rated the pretreatment samples scored the posttreatment samples using transcription and multiple-choice scoring formats. An additional expert listener, blinded to sampling time, scored pre- and posttreatment samples. Results: The posttreatment samples were found to be stable over sampling times for the group. Posttreatment intelligibility scores were statistically significantly higher than the pretreatment scores for both scoring methods (i.e., increases of 9%–10%). Scores derived from the two scoring methods were strongly, positively correlated, with multiple-choice scores being significantly higher than transcription. The scoring methods did not differ significantly in the amount of change found from pre- to posttreatment. There were no statistically significant correlations between AOS severity and changes in pre- to posttreatment intelligibility scores. Performance for most participants was similar to group performance. Conclusions: Stability of posttreatment intelligibility samples supports use of intelligibility scores as outcome measures. This group of speakers demonstrated statistically significant increases in single-word speech intelligibility following sound production treatment. Supplemental Material: https://doi.org/10.23641/asha.26972425