Correspondence between EQ-5D health state classifications and EQ VAS scores

David K Whynes, The TOMBOLA (Trial Of Management of Borderline and Other Low-grade Abnormal smears) Group

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Abstract

BACKGROUND: The EQ-5D health-related quality of life instrument comprises a health state classification followed by a health evaluation using a visual analogue scale (VAS). The EQ-5D has been employed frequently in economic evaluations, yet the relationship between the two parts of the instrument remains ill-understood. In this paper, we examine the correspondence between VAS scores and health state classifications for a large sample, and identify variables which contribute to determining the VAS scores independently of the health states as classified. METHODS: A UK trial of management of low-grade abnormalities detected on screening for cervical pre-cancer (TOMBOLA) provided EQ-5D data for over 3,000 women. Information on distress and multi-dimensional health locus of control had been collected using other instruments. A linear regression model was fitted, with VAS score as the dependent variable. Independent variables comprised EQ-5D health state classifications, distress, locus of control, and socio-demographic characteristics. Equivalent EQ-5D and distress data, collected at twelve months, were available for over 2,000 of the women, enabling us to predict changes in VAS score over time from changes in EQ-5D classification and distress. RESULTS: In addition to EQ-5D health state classification, VAS score was influenced by the subject's perceived locus of control, and by her age, educational attainment, ethnic origin and smoking behaviour. Although the EQ-5D classification includes a distress dimension, the independent measure of distress was an additional determinant of VAS score. Changes in VAS score over time were explained by changes in both EQ-5D severities and distress. Women allocated to the experimental management arm of the trial reported an increase in VAS score, independently of any changes in health state and distress. CONCLUSION: In this sample, EQ VAS scores were predictable from the EQ-5D health state classification, although there also existed other group variables which contributed systematically and independently towards determining such scores. These variables comprised psychological disposition, socio-demographic factors such as age and education, clinically-important distress, and the clinical intervention itself. TRIAL REGISTRATION: ISRCTN34841617.
Original languageEnglish
Article number94
JournalHealth and Quality of Life Outcomes
Volume6
DOIs
Publication statusPublished - 2008

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Keywords

  • Adult
  • Age Factors
  • Algorithms
  • Anxiety
  • Demography
  • Educational Status
  • Female
  • Great Britain
  • Humans
  • Internal-External Control
  • Logistic Models
  • Mass Screening
  • Middle Aged
  • Pain Measurement
  • Precancerous Conditions
  • Psychometrics
  • Quality of Life
  • Risk-Taking
  • Selection Bias
  • Sickness Impact Profile
  • Smoking
  • Uterine Cervical Neoplasms
  • Vaginal Smears

Cite this

Whynes, D. K., & The TOMBOLA (Trial Of Management of Borderline and Other Low-grade Abnormal smears) Group (2008). Correspondence between EQ-5D health state classifications and EQ VAS scores. Health and Quality of Life Outcomes, 6, [94]. https://doi.org/10.1186/1477-7525-6-94