Proportional-odds models for repeated composite and long ordinal outcome scales. 2013

Nick R Parsons
Warwick Medical School, The University of Warwick, Coventry, CV4 7AL, UK. nick.parsons@warwick.ac.uk

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.

UI MeSH Term Description Entries
D003198 Computer Simulation Computer-based representation of physical systems and phenomena such as chemical processes. Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D003627 Data Interpretation, Statistical Application of statistical procedures to analyze specific observed or assumed facts from a particular study. Data Analysis, Statistical,Data Interpretations, Statistical,Interpretation, Statistical Data,Statistical Data Analysis,Statistical Data Interpretation,Analyses, Statistical Data,Analysis, Statistical Data,Data Analyses, Statistical,Interpretations, Statistical Data,Statistical Data Analyses,Statistical Data Interpretations
D006615 Hip The projecting part on each side of the body, formed by the side of the pelvis and the top portion of the femur. Coxa,Coxas,Hips
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D016015 Logistic Models Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor. Logistic Regression,Logit Models,Models, Logistic,Logistic Model,Logistic Regressions,Logit Model,Model, Logistic,Model, Logit,Models, Logit,Regression, Logistic,Regressions, Logistic
D016896 Treatment Outcome Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series. Rehabilitation Outcome,Treatment Effectiveness,Clinical Effectiveness,Clinical Efficacy,Patient-Relevant Outcome,Treatment Efficacy,Effectiveness, Clinical,Effectiveness, Treatment,Efficacy, Clinical,Efficacy, Treatment,Outcome, Patient-Relevant,Outcome, Rehabilitation,Outcome, Treatment,Outcomes, Patient-Relevant,Patient Relevant Outcome,Patient-Relevant Outcomes
D019644 Arthroplasty, Replacement, Hip Replacement of the hip joint. Hip Prosthesis Implantation,Hip Replacement, Total,Total Hip Arthroplasty,Arthroplasties, Hip Replacement,Arthroplasties, Replacement, Hip,Arthroplasty, Hip Replacement,Hip Replacement Arthroplasties,Hip Replacement Arthroplasty,Replacement Arthroplasties, Hip,Replacement Arthroplasty, Hip,Replacement, Total Hip,Total Hip Replacement,Arthroplasty, Total Hip,Hip Arthroplasty, Total,Hip Prosthesis Implantations,Implantation, Hip Prosthesis,Prosthesis Implantation, Hip,Total Hip Arthroplasties,Total Hip Replacements
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