title: Item response theory was used to shorten EORTC QLQ-C30 scales for use in palliative care.
abstract: OBJECTIVE
  The goal was to develop a shortened version of the EORTC QLQ-C30 for use in palliative care. We wanted to keep as few items as possible in each scale while still being able to compare results with studies using the original scales. We examined the possibilities of shortening the physical functioning, cognitive functioning, fatigue, and nausea and vomiting scales.
  
  
  METHODS
  The shortening was based on 2,366 (physical functioning) and 10,815 (three other scales) observations, respectively. We used item response theory to construct scoring algorithms for predicting scores on the original scales.
  
  
  RESULTS
  Evaluations showed that a three-item physical scale, a two-item fatigue scale, and a one-item nausea or vomiting scale predicted the scores on the original scales with excellent agreement and had measurement abilities similar to the original scales with no loss or only a little loss in power to detect group differences. The results of the cognitive functioning scale indicated problems when predicting scores from a shortened version.
  
  
  CONCLUSIONS
  Given the favorable results for the physical functioning, fatigue, and nausea or vomiting scales we expect that the shortened versions of these scales will be included in the abbreviated version of the EORTC QLQ-C30 for palliative care.
authors.affiliation: The Research Unit, Department of Palliative Medicine, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark. map01@bbh.hosp.dk
authors.forename: Morten Aa
authors.initials: MA
authors.lastname: Petersen
authors.forename: Mogens
authors.initials: M
authors.lastname: Groenvold
authors.forename: Neil
authors.initials: N
authors.lastname: Aaronson
authors.forename: Jane
authors.initials: J
authors.lastname: Blazeby
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Brandberg
authors.forename: Alexander
authors.initials: A
authors.lastname: de Graeff
authors.forename: Peter
authors.initials: P
authors.lastname: Fayers
authors.forename: Eva
authors.initials: E
authors.lastname: Hammerlid
authors.forename: Mirjam
authors.initials: M
authors.lastname: Sprangers
authors.forename: Galina
authors.initials: G
authors.lastname: Velikova
authors.forename: Jakob B
authors.initials: JB
authors.lastname: Bjorner
mesh_terms: D003071:Cognition; D005163:Factor Analysis, Statistical; D005221:Fatigue; D006801:Humans; D007802:Language; D015233:Models, Statistical; D009325:Nausea / Q000503:physiopathology; D009369:Neoplasms / Q000503:physiopathology / Q000523:psychology / Q000628:therapy*; D010166:Palliative Care / Q000379:methods*; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D014839:Vomiting / Q000503:physiopathology