title: An analysis of the complementarity of ICECAP-A and EQ-5D-3 L in an adult population of patients with knee pain.
abstract: BACKGROUND
  The ICECAP measures potentially offer a broader assessment of quality of life and well-being, in comparison to measures routinely used in economic evaluation, such as the EQ-5D-3 L. This broader assessment may allow measurement of the full effects of an intervention or treatment. Previous research has indicated that the ICECAP-O (for older people) and EQ-5D-3 L measure provide complementary information. This paper aims to determine similar information for the ICECAP-A (for the entire adult population) in terms of whether the measure is a substitute or complement to the EQ-5D-3 L.
  
  
  METHODS
  Data from the BEEP trial - a multi-centre, pragmatic, randomised controlled trial - were used. Spearman rank correlations and exploratory factor analytic methods were used to assess whether ICECAP-A and EQ-5D-3 L are measuring the same, or different, constructs.
  
  
  RESULTS
  A correlation of 0.49 (p < 0.01) was found between the ICECAP-A tariff score and the EQ-5D-3 L index. Using the pooled items of the EQ-5D-3 L and the ICECAP-A a two factor solution was optimal, with the majority of EQ-5D-3 L items loading onto one factor and the majority of ICECAP-A items onto another.
  
  
  CONCLUSIONS
  The results presented in this paper indicate that ICECAP-A and EQ-5D-3 L are measuring two different constructs and provide largely different, complementary information. Results showed a similarity to results presented by Davis et al. using the ICECAP-O.
  
  
  BACKGROUND
  ISRCTN 93634563.
authors.affiliation: MRC Midland Hub for Trials Methodology Research, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. t.j.h.keeley@bham.ac.uk.|Health Economics Unit, Institute of Applied Health Research, Public Health Building, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. t.j.h.keeley@bham.ac.uk.
authors.forename: T
authors.initials: T
authors.lastname: Keeley
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, BS8 2PS, UK.
authors.forename: J
authors.initials: J
authors.lastname: Coast
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: E
authors.initials: E
authors.lastname: Nicholls
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: N E
authors.initials: NE
authors.lastname: Foster
authors.affiliation: Health Economics Unit, Institute of Applied Health Research, Public Health Building, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.|Arthritis Research UK Primary Care Centre, Research Institute for Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: S
authors.initials: S
authors.lastname: Jowett
authors.affiliation: Health Economics Unit, Institute of Applied Health Research, Public Health Building, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: H
authors.initials: H
authors.lastname: Al-Janabi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007717:Knee; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000523:psychology*; D010147:Pain Measurement / Q000295:instrumentation*; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires