Dual scales for the evaluation of verbal and communication skills in individuals with aphasia: a preliminary study

Background Assessing individuals with aphasia requires tools that address both language impairments and functional communication – the ability to convey messages effectively through verbal, nonverbal and compensatory strategies when speech production is impaired. While existing assessments often measure these dimensions separately, this study developed and validated two easy-to-administer rating scales based on the Measurement of Participation in Conversation (MPC) interaction framework by Kagan et al. (2004).Aims (a) determine whether the proposed dual rating scales independently and reliably captured both verbal proficiency and functional communication in individuals with aphasia during the same tasks, and examine the construct validity of the scales. (b) determine the consistency in rating patterns between experienced speech-language pathologists (SLPs) and naive raters during communicative assessment.Methods & Procedures To test the validity and reliability of the dual scales, raters assessed six individuals with aphasia on two task types: picture-based storytelling monologue and open-ended conversational prompts. Thirty-nine SLPs across four rehabilitation centers evaluated both verbal proficiency and functional communication, while 41 individuals without prior familiarity with aphasia (naive raters) evaluated functional communication only. Construct validity of the scales was tested by assessing correlations between the ratings of the evaluators and the percent word retrieval measure (%WR).Outcomes & Results Results were compared within and between rater groups as well as across and within tasks. The results indicated moderate internal consistency across tasks, suggesting each task draws on different communicative skills. Inter-rater reliability was moderate to high overall, with greater consistency observed among SLPs. In contrast, naive raters demonstrated greater score variability and lower agreement, suggesting reliance on surface-level cues due to limited familiarity with aphasia. Despite scoring differences, both rater groups demonstrated general agreement on performance rankings, supporting the reliability of the scales. Notably, on average, SLPs rated individuals with aphasia more favorably than naive raters, indicating the scales are particularly effective when used by trained professionals who can identify communicative strengths not apparent to untrained observers. Individuals with aphasia were relatively homogeneous in some language domains, such as semantic processing, but were varied in severity and in others including phonology and syntax. Strong correlations were found between the ratings of both scales and the %WR measure. Limitations include the need for broader representation of aphasia types and further investigation of how SLP experience levels may influence scale use. Overall, the proposed scales offer a promising approach for capturing both verbal performance and functional communication in clinical settings.