title: Revealing response shift in longitudinal research on fatigue--the use of the thentest approach.
abstract: In this study we examined whether response shift resulting from changes in internal standards occurs in cancer patients undergoing radiotherapy. Ninety-nine newly diagnosed patients undergoing radiotherapy were administered two standardized self-report measures of fatigue prior to receiving radiotherapy. After completion of radiotherapy, patients filled out these questionnaires as a conventional posttest and in reference to how they perceived themselves as they were prior to radiotherapy (a so-called 'thentest'). A transition (direct change) score on fatigue was used as a stratification measure. Patients were subsequently interviewed about their responses. The pattern of mean scores indicative of response-shift effects was found in two distinct subgroups: patients experiencing diminishing levels of fatigue and patients facing early stages of adaptation to increased levels of fatigue. Since response shift may adversely affect the results of self-reported outcomes in clinical trials or other longitudinal research, further research is very much needed.
authors.affiliation: Academic Medical Center, Amsterdam, The Netherlands. m.a.sprangers@amc.uva.nl
authors.forename: M A
authors.initials: MA
authors.lastname: Sprangers
authors.forename: F S
authors.initials: FS
authors.lastname: Van Dam
authors.forename: J
authors.initials: J
authors.lastname: Broersen
authors.forename: L
authors.initials: L
authors.lastname: Lodder
authors.forename: L
authors.initials: L
authors.lastname: Wever
authors.forename: M R
authors.initials: MR
authors.lastname: Visser
authors.forename: P
authors.initials: P
authors.lastname: Oosterveld
authors.forename: E M
authors.initials: EM
authors.lastname: Smets
mesh_terms: D000223:Adaptation, Psychological; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003710:Demography; D005221:Fatigue / Q000209:etiology / Q000523:psychology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000523:psychology / Q000532:radiotherapy*; D012015:Reference Standards; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012959:Socioeconomic Factors