Validating the Communicative Participation Item Bank (CPIB) for use with people with aphasia: an analysis of Differential Item Function (DIF).
Carolyn Baylor, Megan Oelke, Alyssa Bamer and 6 others
PMID 30918415WHAT IT FOUND
The CPIB appears usable with people with aphasia without needing different scoring, but family proxy ratings do not match self-report.
Clinicians may need to provide communication support.
Key findings
01The main bias checks found no CPIB items behaved differently for people with aphasia; the 5% change in beta check found two items, but scores adjusted for this were essentially identical to scores not adjusted.
02The WAB-R Aphasia Quotient appeared likely to allow relatively independent CPIB completion at scores of 80 or higher, while scores below 50 may make completion difficult.
03On the CPIB T-score scale, proxy short-form scores averaged 41.8, while self-reported short-form scores averaged 47.1, and the correlation between self and proxy scores was 0.255.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample size of 110 people with aphasia was lower than recommended for differential item functioning analyses, and the authors called the validation results preliminary. Seven participants were removed because they could not complete enough CPIB items, so some people with severe aphasia may not be represented in the analysed sample. The study used the full 46-item CPIB bank for validation. Routine use would use the 10-item short form or an adaptive format, so the assistance levels reported here may overstate what is needed in practice. Communication supports were necessary, but they carry a risk that examiner explanations could change item meaning. The authors noted this as a limitation of patient-reported outcome administration. Proxy ratings were collected for 90 participants, and proxies were instructed to report their own view of the person's participation rather than guess how the person would answer.
The easy way to misread this
Do not use family or caregiver proxy CPIB scores as a substitute for the person with aphasia's own report. In this study, proxy scores correlated only 0.255 with self-reported scores, and proxies rated communicative participation more negatively.