title: Validity and responsiveness of the EQ-5D in assessing and valuing health status in patients with somatoform disorders.
abstract: BACKGROUND
  The EQ-5D is a generic questionnaire providing a preference-based index score applicable to cost-utility analysis. This is the first study to validate the EQ-5D in patients with somatoform disorders.
  
  
  METHODS
  Data of the EQ-5D descriptive system, the British and the German EQ-5D index and the EQ Visual Analogue Scale, the Patient Health Questionnaire 15, the Patient Health Questionnaire 9, the Whiteley Index 7 and the Short Form 36 were collected from 294 patients at baseline, 244 at 6 months and 256 at 12 months after baseline. The discriminative ability of the EQ-5D was evaluated by comparison with a general population sample and by the ability to distinguish between different symptom severities. Convergent validity was analysed by assessing associations between the EQ-5D and the other instruments. Responsiveness was evaluated by analysing the effects on scores between two measurements in groups of patients reporting worse, same or better health. The Bonferroni correction was employed.
  
  
  RESULTS
  For all items of the EQ-5D except 'self-care', patients with somatoform disorders reported more problems than the general population. The EQ-5D showed discriminative ability in patients with different symptom severities. For nearly all reference instruments there were significant differences in mean scores between respondents with and without problems in the various EQ-5D items and strong correlations with the EQ Visual Analogue Scale and the EQ-5D index scores. Evidence for the responsiveness of the EQ-5D could only be found for patients with better health; effects were medium at the utmost.
  
  
  CONCLUSIONS
  The EQ-5D showed a considerable validity and a limited responsiveness in patients with somatoform disorders.
  
  
  BACKGROUND
  Current Controlled Trials ISRCTN55280791.
authors.affiliation: Department of Medical Sociology and Health Economics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. c.brettschneider@uke.de
authors.forename: Christian
authors.initials: C
authors.lastname: Brettschneider
authors.forename: Hans-Helmut
authors.initials: HH
authors.lastname: König
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Herzog
authors.forename: Claudia
authors.initials: C
authors.lastname: Kaufmann
authors.forename: Rainer
authors.initials: R
authors.lastname: Schaefert
authors.forename: Alexander
authors.initials: A
authors.lastname: Konnopka
mesh_terms: D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D011581:Psychological Tests; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013001:Somatoform Disorders / Q000175:diagnosis* / Q000523:psychology; D011795:Surveys and Questionnaires / Q000592:standards