title: Interpretation of differential item functioning analyses using external review.
abstract: Differential item functioning (DIF) analyses are used to determine whether certain groups respond differently to a particular item of a test or questionnaire; however, these do not explain the reasons for observed response differences. Many studies have used external reviews of items, sometimes using blinded reviewers, to help interpret these results. The authors conducted a literature review of this topic to describe the current usage of external reviews alongside DIF analyses. It concentrated on studies of health-related quality of life instruments, but studies in other fields were also considered. Relatively few examples of blinded item reviews were identified, and these were mostly from educational studies. A case study using blinded bilingual reviewers alongside translation DIF analyses of a health-related quality of life instrument is described. Future researchers should consider conducting external item reviews alongside DIF analyses.
authors.affiliation: Section of Population Health, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen, AB25 2ZD, UK. n.w.scott@abdn.ac.uk
authors.forename: Neil W
authors.initials: NW
authors.lastname: Scott
authors.forename: Peter M
authors.initials: PM
authors.lastname: Fayers
authors.forename: Neil K
authors.initials: NK
authors.lastname: Aaronson
authors.forename: Andrew
authors.initials: A
authors.lastname: Bottomley
authors.forename: Alexander
authors.initials: A
authors.lastname: de Graeff
authors.forename: Mogens
authors.initials: M
authors.lastname: Groenvold
authors.forename: Chad
authors.initials: C
authors.lastname: Gundy
authors.forename: Michael
authors.initials: M
authors.lastname: Koller
authors.forename: Morten A
authors.initials: MA
authors.lastname: Petersen
authors.forename: Mirjam A G
authors.initials: MA
authors.lastname: Sprangers
mesh_terms: D003431:Cross-Cultural Comparison; D006801:Humans; D015588:Observer Variation; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011788:Quality of Life; D011795:Surveys and Questionnaires