Applying mixed methods to pretest the Pressure Ulcer Quality of Life (PU-QOL) instrument
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Pretesting is key in the development of patient-reported outcome (PRO) instruments. We describe a mixed-methods approach based on interviews and Rasch measurement methods in the pretesting of the Pressure Ulcer Quality of Life (PU-QOL) instrument.
We used cognitive interviews to pretest the PU-QOL in 35 patients with pressure ulcers with the view to identifying problematic items, followed by Rasch analysis to examine response options, appropriateness of the item series and biases due to question ordering (item fit). We then compared findings in an interactive and iterative process to identify potential strengths and weaknesses of PU-QOL items, and guide decision-making about further revisions to items and design/layout.
Although cognitive interviews largely supported items, they highlighted problems with layout, response options and comprehension. Findings from the Rasch analysis identified problems with response options through reversed thresholds.
The use of a mixed-methods approach in pretesting the PU-QOL instrument proved beneficial for identifying problems with scale layout, response options and framing/wording of items. Rasch measurement methods are a useful addition to standard qualitative pretesting for evaluating strengths and weaknesses of early stage PRO instruments.
KeywordsPressure ulcer Health-related quality of life Patient-reported outcome Mixed methods
Health-related quality of life
The authors would like to thank the outcome methodologists: Sara Schroter, Katerina Hilari, Yasmene Alavi, Jennifer Petrillo, and the clinical experts: Lyn Wilson, Elizabeth McGinnis, E Andrea Nelson, Nikki Stubbs, Susanne Coleman, Michelle Briggs, Carol Dealey for participation in the appraisal process. Financial support was provided by the National Institute for Health Research (NIHR) under its Programme Grants for Applied Research funding scheme (RP-PG-0407-10056). The views and opinions expressed within this article are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.
Conflict of interest
The authors declare that they have no conflict of interest.
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