Use of ordinal outcomes in vascular prevention trials: comparison with binary outcomes in published trials

Bath, Philip M.W. and Geeganage, Chamila and Gray, Laura J. and Collier, T and Pocock, S (2008) Use of ordinal outcomes in vascular prevention trials: comparison with binary outcomes in published trials. Stroke . ISSN 1524-4628

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Abstract

Background and Purpose—Vascular prevention trials mostly count “yes/no” (binary) outcome events, eg, stroke/no

stroke. Analysis of ordered categorical vascular events (eg, fatal stroke/nonfatal stroke/no stroke) is clinically relevant

and could be more powerful statistically. Although this is not a novel idea in the statistical community, ordinal outcomes

have not been applied to stroke prevention trials in the past.

Methods—Summary data on stroke, myocardial infarction, combined vascular events, and bleeding were obtained by

treatment group from published vascular prevention trials. Data were analyzed using 10 statistical approaches which

allow comparison of 2 ordinal or binary treatment groups. The results for each statistical test for each trial were then

compared using Friedman 2-way analysis of variance with multiple comparison procedures.

Results—Across 85 trials (335 305 subjects) the test results differed substantially so that approaches which used the ordinal

nature of stroke events (fatal/nonfatal/no stroke) were more efficient than those which combined the data to form 2

groups (P0.0001). The most efficient tests were bootstrapping the difference in mean rank, Mann–Whitney U test, and

ordinal logistic regression; 4- and 5-level data were more efficient still. Similar findings were obtained for myocardial

infarction, combined vascular outcomes, and bleeding. The findings were consistent across different types, designs and

sizes of trial, and for the different types of intervention.

Conclusions—When analyzing vascular events from prevention trials, statistical tests which use ordered categorical data

are more efficient and are more likely to yield reliable results than binary tests. This approach gives additional

information on treatment effects by severity of event and will allow trials to be smaller. (Stroke. 2008;39:000-000.)

Item Type: Article
Schools/Departments: University of Nottingham UK Campus > Faculty of Medicine and Health Sciences > School of Medicine > Division of Clinical Neuroscience
Depositing User: Sayers, Hazel
Date Deposited: 19 Sep 2008 09:51
Last Modified: 14 Aug 2013 13:37
URI: http://eprints.nottingham.ac.uk/id/eprint/961

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