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Proportional-odds models for repeated composite and long ordinal outcome scales
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Parsons, Nicholas R. (2013) Proportional-odds models for repeated composite and long ordinal outcome scales. Statistics in Medicine, Volume 32 (Number 18). pp. 3181-3191. doi:10.1002/sim.5756 ISSN 0277-6715.
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Official URL: http://dx.doi.org/10.1002/sim.5756
Abstract
In many medical studies, researchers widely use composite or long ordinal scores, that is, scores that have a large number of categories and a natural ordering often resulting from the sum of a number of short ordinal scores, to assess function or quality of life. Typically, we analyse these using unjustified assumptions of normality for the outcome measure, which are unlikely to be even approximately true. Scores of this type are better analysed using methods reserved for more conventional (short) ordinal scores, such as the proportional-odds model. We can avoid the need for a large number of cut-point parameters that define the divisions between the score categories for long ordinal scores in the proportional-odds model by the inclusion of orthogonal polynomial contrasts. We introduce the repeated measures proportional-odds logistic regression model and describe for long ordinal outcomes modifications to the generalized estimating equation methodology used for parameter estimation. We introduce data from a trial assessing two surgical interventions, briefly describe and re-analyse these using the new model and compare inferences from the new analysis with previously published results for the primary outcome measure (hip function at 12 months postoperatively). We use a simulation study to illustrate how this model also has more general application for conventional short ordinal scores, to select amongst competing models of varying complexity for the cut-point parameters.
Item Type: | Journal Article | ||||
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Subjects: | R Medicine > RA Public aspects of medicine | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School > Health Sciences Faculty of Science, Engineering and Medicine > Medicine > Warwick Medical School |
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Library of Congress Subject Headings (LCSH): | Health status indicators, Orthogonal polynomials, Generalized estimating equations | ||||
Journal or Publication Title: | Statistics in Medicine | ||||
Publisher: | John Wiley & Sons Ltd. | ||||
ISSN: | 0277-6715 | ||||
Official Date: | 2013 | ||||
Dates: |
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Volume: | Volume 32 | ||||
Number: | Number 18 | ||||
Number of Pages: | 11 | ||||
Page Range: | pp. 3181-3191 | ||||
DOI: | 10.1002/sim.5756 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Date of first compliant deposit: | 23 March 2016 | ||||
Date of first compliant Open Access: | 23 March 2016 |
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