A comparative study of signal versus aggregate methods of outcome measurement based on the WOMAC Osteoarthritis Index. Western Ontario and McMaster Universities Osteoarthritis Index. Academic Article uri icon

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  • OBJECTIVE: To compare signal versus aggregate measurement strategies using the VA3.0S version of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis (OA) Index. METHODS: Seventy patients with OA of the knee were asked to identify a signal item for each of the 3 dimensions of the WOMAC OA Index at baseline and termination of a 12-week, double blind, randomized, controlled trial. RESULTS: The signal method detected statistically significant alterations in health status at relatively small sample sizes and with a relative efficiency close to or at unity. In addition to a low prevalence of deterioration in nonsignal items, we observed some inconsistency in signal selection. CONCLUSION: Signal methods of measurement may provide an alternative approach to outcome measurement provided issues of nonsignal deterioration and the consistency of signal selection can be addressed.


  • Barr, S
  • Bellamy, N
  • Buchanan, WW
  • Chalmers, A
  • Ford, PM
  • Kean, Walter
  • Kraag, GR
  • Gerecz-Simon, E
  • Campbell, J

publication date

  • November 1994