title: Applying mixed methods to pretest the Pressure Ulcer Quality of Life (PU-QOL) instrument.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Clinical Trials Research Unit (CTRU), University of Leeds, Leeds, LS2 9JT, UK. c.gorecki@leeds.ac.uk
authors.forename: C
authors.initials: C
authors.lastname: Gorecki
authors.forename: D L
authors.initials: DL
authors.lastname: Lamping
authors.forename: J
authors.initials: J
authors.lastname: Nixon
authors.forename: J M
authors.initials: JM
authors.lastname: Brown
authors.forename: S
authors.initials: S
authors.lastname: Cano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004739:England; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D008875:Middle Aged; D003668:Pressure Ulcer / Q000503:physiopathology / Q000523:psychology*; D011594:Psychometrics; D011788:Quality of Life; D012107:Research Design; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires