Validating the Communicative Participation Item Bank (CPIB) for use with people with aphasia: an analysis of differential item function (DIF)

Background: The term “communicative participation” refers to participation in the communication aspects of life roles at home, at work and in social and leisure situations. Participation in life roles is a key element in biopsychosocial frameworks of health, such as the World Health Organization’s International Classification of Functioning, Disability and Health (ICF) and the Aphasia Framework for Outcomes Measurement. The Communicative Participation Item Bank (CPIB) was developed as a patient-reported measure of communicative participation for adults. Initial validation focused on adults with motor speech or voice disorders. No prior studies have conducted quantitative validation analyses for the CPIB for people with aphasia (PWA). Aims: The primary purpose of this study was to begin validation of the CPIB for PWA by conducting an analysis of differential item functioning (DIF). A DIF analysis was used to identify whether item parameters of the CPIB differed between PWA and the populations used in prior CPIB calibration. Secondary analyses evaluated the level of assistance needed by PWA to complete the CPIB, relationships between the CPIB and a gold-standard patient-reported instrument for PWA—American Speech-Language-Hearing Association Quality of Communication Life Scale (ASHA-QCL) and relationships between PWA and family proxy report on the CPIB. Methods & Procedures: This study included 110 PWA and 90 proxy raters. PWA completed a battery of patient-reported questionnaires in one face-to-face session. Speech-language pathologists provided communication support. Data on aphasia severity from the Western Aphasia Battery—Revised (WAB-R) and demographic data either existed from prior research or were collected during the session. Proxy raters completed a similar battery of self-report questionnaires. Outcomes & Results: Results of the DIF analysis suggested statistically significant DIF on two of the 46 items in the CPIB, but the DIF had essentially no impact on CPIB scores. PWA with WAB-R Aphasia Quotient scores above 80 appeared comfortable reading the CPIB items, although required occasional assistance. Most participants who were unable to complete the CPIB had WAB-R Aphasia Quotient scores lower than 50. Correlation between the CPIB and ASHA-QCL was moderate; and correlation between PWA and proxy scores was low. Conclusions: Most PWA were able to respond to CPIB items, although most required or requested support. Although these results are preliminary due to a small sample size, the data support that the CPIB may be valid for PWA. Caution is warranted regarding proxy report because of low correlation between PWA and proxy ratings.