Abstract
PURPOSE: The Multilevel word Accuracy Composite Scale (MACS) is a novel whole-word measure of speech production accuracy designed to evaluate behaviors commonly targeted in motor-based intervention for childhood apraxia of speech (CAS). The MACS yields a composite score generated through ratings of segmental accuracy, word structure maintenance, prosody, and movement transition. This study examined the validity of the MACS through comparison to established measures of speech accuracy. Reliability was also examined within and between practicing speech-language pathologists (SLPs). METHOD: The MACS was used to rate 117 tokens produced by children with severe CAS. Ratings were performed in the laboratory setting by two expert raters and by practicing SLPs (N = 19). Concurrent validity was estimated through comparison of expert MACS ratings (i.e., MACS score and each component rating) to measures of speech accuracy (percent phoneme correct and the 3-point scale) using correlational analyses. Reliability was examined between expert raters and across SLP raters using the intraclass correlation coefficient to examine interrater reliability of expert ratings, in addition to inter- and intrarater reliability of SLP ratings. RESULTS: Correlation analyses between MACS ratings (i.e., MACS score and component ratings) and existing measures of speech accuracy revealed small to large positive correlations between measures. Reliability analyses revealed moderate to excellent reliability for MACS ratings performed by expert raters and between (interrater) and within (intrarater) SLP raters. CONCLUSIONS: Analyses of concurrent validity indicate that the MACS aligns with established measures, yet contributes novel elements for rating speech accuracy. Results further support the MACS as a reliable measure for rating speech accuracy in children with severe speech impairment for ratings performed by expert raters and practicing clinicians.