title: Psychometric comparison of the standard EQ-5D to a 5 level version in cancer patients.
abstract: OBJECTIVE
  The objectives of this study were: 1) to determine whether expanding the number of levels (ie, response categories) on the standard 3 level EQ-5D (EQ-5D-3L) to 5-levels (EQ-5D-5L) would improve the descriptive richness and ability of the measure to discriminate among different levels of health, and 2) to examine the psychometric properties of each EQ-5D version in patients with cancer.
  
  
  METHODS
  U.S.-based cancer patients self-assessed their health using EQ-5D-3L and EQ-5D-5L. These versions were compared in terms of ceiling effects, convergent validity based on correlations with ECOG performance status and FACT-G, discriminative ability using Rasch analysis, and informational richness using Shannon's Evenness Index (J').
  
  
  RESULTS
  A ceiling effect was observed among a greater proportion of respondents to EQ-5D-3L, n=74/424 (17%), compared with EQ-5D-5L, n=47/424 (11%). Within the midlevel of EQ-5D-3L (some problems), substantial partitioning of the sample into the 3 nonextreme levels of the EQ-5D-5L was observed across dimensions. EQ-5D-5L demonstrated a trend towards slightly stronger correlations with ECOG performance status compared with EQ-5D-3L for all dimensions of health, ie, rs (5L/3L): rmobility=0.38/0.31; rself-care=0.35/0.31; rusual activities=0.55/0.47; rpain/discomfort=0.43/0.37; ranxiety/depression=0.23/0.16; rcrude summary score=0.56/0.49. EQ-5D-5L demonstrated a greater relative efficiency and ability to discriminate different levels of health. Informational richness and evenness of EQ-5D-5L was slightly higher (J'5L=0.75) than EQ-5D-3L (J'3L=0.69).
  
  
  CONCLUSIONS
  Evidence supported the validity of both EQ-5D-3L and EQ-5D-5L in cancer. However, results suggest a 5-level classifier system has less ceiling effect and greater discriminative ability with potentially more power to detect differences between groups compared with EQ-5D-3L.
authors.affiliation: Center for Pharmacoeconomic Research and Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago 60612, and Midwest Center for Health Services and Policy Research, Hines VA Hospital, Hines, Illinois, USA. pickard1@uic.edu
authors.forename: A Simon
authors.initials: AS
authors.lastname: Pickard
authors.forename: Maria C
authors.initials: MC
authors.lastname: De Leon
authors.forename: Thomas
authors.initials: T
authors.lastname: Kohlmann
authors.forename: David
authors.initials: D
authors.lastname: Cella
authors.forename: Sarah
authors.initials: S
authors.lastname: Rosenbloom
mesh_terms: D000203:Activities of Daily Living / Q000523:psychology; D003863:Depression / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000523:psychology*; D010146:Pain / Q000523:psychology; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D012648:Self Care / Q000523:psychology; D011795:Surveys and Questionnaires