title: The validity of the EQ-5D-3L items: an investigation with type 2 diabetes patients from six European countries.
abstract: BACKGROUND
  Most previous studies concerning the validity of the EQ-5D-3L items refer to applications of only a single language version of the EQ-5D-3L in only one country. Therefore, there is little information concerning the extent to which the results can be generalised across different language versions and/or different countries. Here the validity of the EQ-5D-3L items is investigated for six different language versions in six different countries.
  
  
  METHODS
  Data came from 1341 type 2 diabetes patients (England: 289; Finland: 177; Germany: 255; Greece: 165; the Netherlands: 354; Spain: 101). The relationships of the five EQ-5D-3L items with seven different test variables (age, gender, education, previous stroke, problems with heart, problems with lower extremities, problems with eyes), were analysed for each combination of item and test variable. For each combination two logistic regression models with the dichotomised EQ-5D-3L item as dependent variable were computed. The first model contained the test variable and dummy coded countries as independent variables, the second model additionally the terms for the interaction between country and test variable. Statistically significant better fit of the second model was taken as evidence for country specific differences regarding the relationship. When such differences could be attributed mainly to one country the analyses were repeated without the data from this country. Validity was investigated with the remaining data using results of the first models.
  
  
  RESULTS
  Due to lack of variation in the Spanish data only 31 of the originally intended 35 interaction tests could be performed. Only three of these yielded a significant result. In all three cases the Spanish data deviated most. Without the Spanish data only 1 of the 35 interaction tests yielded a significant result. With 3 exceptions, the tendency of reporting problems increased with age, female gender, lower education, previous stroke, heart problems, problems with lower extremities and problems with eyes for all EQ-5D-3L items.
  
  
  CONCLUSIONS
  The results concerning the European Spanish version are ambiguous. However, the items of the English, Finnish, German, Greek and Dutch versions of the EQ-5D-3L relate in substantially the same way to the test variables. Mostly, these relationships indicate the items' validity.
authors.affiliation: Trimberg Research Academy, University of Bamberg, Bamberg, D-96045, Germany. uwe.konerding@uni-bamberg.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Konerding
authors.affiliation: Institute of Health Policy & Management, Erasmus University Rotterdam, PO Box 1738, Rotterdam, DR, 3000, The Netherlands. elkhuizen@bmg.eur.nl.
authors.forename: Sylvia G
authors.initials: SG
authors.lastname: Elkhuizen
authors.affiliation: Joint Research Unit in Biomedical Engineering, IIS La Fe- Universitat Politècnica de València, Bulevar sur s/n, 46026, Valencia, Spain. rfaubel@itaca.upv.es.
authors.forename: Raquel
authors.initials: R
authors.lastname: Faubel
authors.affiliation: The Balance of Care Group, 39a Cleveland Road, London, N1 3ES, UK. paul@paul40.demon.co.uk.
authors.forename: Paul
authors.initials: P
authors.lastname: Forte
authors.affiliation: Department of Industrial Engineering and Management, Aalto University, PO Box 15500, Espoo, Aalto, 00076, Finland. tomi.malmstrom@aalto.fi.
authors.forename: Tomi
authors.initials: T
authors.lastname: Malmström
authors.affiliation: Department of Health Economics, National School of Public Health, 196 Alexandras Ave, 115 21, Athens, Greece. epavi@esdy.edu.gr.
authors.forename: Elpida
authors.initials: E
authors.lastname: Pavi
authors.affiliation: Department of Psychiatry, Section Medical Psychology & Psychotherapy, Erasmus MC, PO Box 2040, CA, 3000, Rotterdam, The Netherlands. mf.bas.janssen@googlemail.com.
authors.forename: M F Bas
authors.initials: MF
authors.lastname: Janssen
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D048909:Diabetes Complications / Q000209:etiology / Q000523:psychology*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000523:psychology*; D004739:England; D005060:Europe; D005260:Female; D005387:Finland; D005858:Germany; D006115:Greece; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009426:Netherlands; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D013030:Spain; D011795:Surveys and Questionnaires