title: Determining clinically important differences in health status measures: a general approach with illustration to the Health Utilities Index Mark II.
abstract: The objective of this article was to describe and illustrate a comprehensive approach for estimating clinically important differences (CIDs) in health-related quality-of-life (HR-QOL). A literature review and pilot study were conducted to determine whether effect size-based benchmarks are consistent with CIDs obtained from other approaches. CIDs may be estimated based primarily upon effect sizes, supplemented by more traditional anchor-based methods of benchmarking (i.e. direct, cross-sectional or longitudinal approaches). A literature review of articles discussing CIDs provided comparative data on effect sizes for various chronic conditions. A pilot study was then conducted to estimate the minimum CID of the Health Utilities Index (HUI) Mark II, and to compare the observed between-group differences observed in a recent randomised trial of an acute stroke intervention with this benchmark. The use of standardised effect size benchmarks has a number of advantages-for example, effect sizes are efficient, widely accepted outside HR-QOL, and have well accepted benchmarks based upon external anchors. In addition, our literature review and pilot study suggest that effect size-based CID benchmarks are similar to those which would be obtained using more traditional methods. For most HR-QOL instruments, we do not know the changes in score which constitute CIDs of various magnitudes. This makes interpretation of HR-QOL results from clinical trials difficult, and having a benchmarking process which is relatively straightforward would be highly desirable.
authors.affiliation: Center for Clinical Health Policy Research, Duke University School of Medicine, Durham, North Carolina, USA. samsa001@mc.duke.edu
authors.forename: G
authors.initials: G
authors.lastname: Samsa
authors.forename: D
authors.initials: D
authors.lastname: Edelman
authors.forename: M L
authors.initials: ML
authors.lastname: Rothman
authors.forename: G R
authors.initials: GR
authors.lastname: Williams
authors.forename: J
authors.initials: J
authors.lastname: Lipscomb
authors.forename: D
authors.initials: D
authors.lastname: Matchar
mesh_terms: D002986:Clinical Trials as Topic / Q000379:methods; D003430:Cross-Sectional Studies; D006305:Health Status Indicators; D006801:Humans; D008137:Longitudinal Studies; D010865:Pilot Projects; D011788:Quality of Life