Adaptation and investigation of validity and reliability measures of the communication outcome after stroke scale (COAST) for Cantonese speakers with aphasia: a preliminary study

Background: There has been a growing interest in applying patient-centered tools for assessing functional communication and its impact on quality of life, which provides important insights into aphasia rehabilitation. The Communication Outcome After Stroke (COAST) scale is among the measures used to study the perceptions of people with aphasia (PWA) on their communication functions in different real-life contexts. Nevertheless, such a clinical tool has been lacking in the Chinese-speaking population. Aim: This preliminary study investigated the psychometric properties (including validity and reliability measures) of the Hong Kong Cantonese version of the Communication Outcome after Stroke (HK-Can-COAST) scale for Cantonese-speaking PWA in Hong Kong. Methods & Procedures: HK-Can-COAST was translated into Chinese from its original English version with cultural adaptations in pictorial illustrations, while the content, presentation, response format, and scoring method were preserved. The 20-item scale, together with two standardized aphasia assessments, was administered to 42 individuals with stroke-induced chronic aphasia twice, with a lapse of three weeks in between. Validity (face, concurrent, and construct validity) and reliability (internal consistency and test-retest reliability) measures of HK-Can-COAST were examined. Outcomes & Results: Initial findings suggested that the psychometric properties of HK-Can-COAST were satisfactory. All questions were regarded as appropriate for evaluating the functional communication of PWA. Excellent internal consistency (α = 0.94) and good test-retest reliability (r = 0.76, ICC = 0.94) were obtained. In terms of concurrent and construct validity, HK-Can-COAST was mildly correlated with aphasia severity and moderately correlated with standardized measures of functional communication. Conclusions: HK-Can-COAST seems to be an appropriate tool for measuring functional communication and its impact on quality of life from a patient’s perspective. Further development involving a larger sample size and a more comprehensive investigation of psychometric properties are warranted.