Statistical analyses of ordinal outcomes in randomised controlled trials: a scoping review.

Publisher: BioMed Central Country of Publication: England NLM ID: 101263253 Publication Model: Electronic Cited Medium: Internet ISSN: 1745-6215 (Electronic) Linking ISSN: 17456215 NLM ISO Abbreviation: Trials

Original Publication: [London] : BioMed Central, 2006-

Randomized Controlled Trials as Topic*/methods ; Randomized Controlled Trials as Topic*/statistics & numerical data ; Research Design*/statistics & numerical data; Humans ; Data Interpretation, Statistical ; Treatment Outcome ; Models, Statistical ; Endpoint Determination

Background: Randomised controlled trials (RCTs) aim to estimate the causal effect of one or more interventions relative to a control. One type of outcome that can be of interest in an RCT is an ordinal outcome, which is useful to answer clinical questions regarding complex and evolving patient states. The target parameter of interest for an ordinal outcome depends on the research question and the assumptions the analyst is willing to make. This review aimed to provide an overview of how ordinal outcomes have been used and analysed in RCTs.
Methods: The review included RCTs with an ordinal primary or secondary outcome published between 2017 and 2022 in four highly ranked medical journals (the British Medical Journal, New England Journal of Medicine, The Lancet, and the Journal of the American Medical Association) identified through PubMed. Details regarding the study setting, design, the target parameter, and statistical methods used to analyse the ordinal outcome were extracted.
Results: The search identified 309 studies, of which 144 were eligible for inclusion. The most used target parameter was an odds ratio, reported in 78 (54%) studies. The ordinal outcome was dichotomised for analysis in 47 ( 33 % ) studies, and the most common statistical model used to analyse the ordinal outcome on the full ordinal scale was the proportional odds model (64 [ 44 % ] studies). Notably, 86 (60%) studies did not explicitly check or describe the robustness of the assumptions for the statistical method(s) used.
Conclusions: The results of this review indicate that in RCTs that use an ordinal outcome, there is variation in the target parameter and the analytical approaches used, with many dichotomising the ordinal outcome. Few studies provided assurance regarding the appropriateness of the assumptions and methods used to analyse the ordinal outcome. More guidance is needed to improve the transparent reporting of the analysis of ordinal outcomes in future trials.
(© 2024. The Author(s).)

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ID 1171422 National Health and Medical Research Council; ID 1035261 National Health and Medical Research Council; ID 1127984 National Health and Medical Research Council; 1159225 National Health and Medical Research Council

Keywords: Ordinal outcomes; Proportional odds model; Randomised controlled trials; Scoping review

Date Created: 20240406 Date Completed: 20240807 Latest Revision: 20240807

20240808

PMC10998402

10.1186/s13063-024-08072-2

38582924