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Trials

Open Access

A win ratio approach to comparing ordinal or non-normal outcomes in clinical trials

  • Duolao Wang1 and
  • Stuart Pocock1
Trials201314(Suppl 1):O47

https://doi.org/10.1186/1745-6215-14-S1-O47

Published: 29 November 2013

Keywords

Hospital StayControl TreatmentFavourable OutcomeTreatment PatientHeart Association

Clinical trials are often designed to compare an ordinal outcome such as New York Heart Association (NYHA) functional classification or a non-Normal outcome such as duration of hospital stay in cardiovascular trials. The conventional statistical method for such a comparison is a non-parametric Mann-Whitney test, which provides a P-value for testing the hypothesis that the distributions of both treatment groups are identical but does not provide an estimate of treatment effect. For that, Hodges and Lehmann proposed estimating the shift parameter between two populations and its confidence interval. However, such a shift parameter does not have a straightforward interpretation and its confidence interval contains zero in some cases when Mann-Whitney test produces significant result.

To overcome the above problems, we introduce the concept of the win ratio for analysing such data. The original use of the win ratio was for a hierarchy of composite time to event outcomes (Pocock et al 2012). Patients in the new and control treatment are formed into all possible pairs. For each pair the new treatment patient is labelled a "winner" or a "loser" if it is known who had a favourable outcome. The win ratio is the total number of winners divided by the total numbers of losers. A 95% CI and P-value for the win ratio are readily obtained. This method is demonstrated by analyses of NYHA in PARTNER B trial and hospital stay in PLACIDE trial. Statistical properties of the win ratio statistic are investigated using simulation studies of non-Normal outcomes under various scenarios.

Authors’ Affiliations

(1)
London School of Hygiene and Tropical Medicine, London, UK

References

  1. Pocock SJ, Ariti CA, Collier TJ, Wang D: The win ratio: a new approach to the analysis of composite endpoints in clinical trials based on clinical priorities. Eur Heart J. 2012, 33 (2): 176-82. 10.1093/eurheartj/ehr352.View ArticlePubMedGoogle Scholar

Copyright

© Wang and Pocock; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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