  Randomised controlled trials aim to assess the impact of one (or more) health
interventions relative to other standard interventions. RCTs sometimes use an
ordinal outcome, which is an endpoint that comprises of multiple, monotonically
ordered categories that are not necessarily separated by a quantifiable
distance. Ordinal outcomes are appealing in clinical settings as disease states
can represent meaningful categories that may be of clinical importance. They
can also retain information and increase statistical power compared to
dichotomised outcomes. Target parameters for ordinal outcomes in RCTs may vary
depending on the nature of the research question, the modelling assumptions,
and the expertise of the data analyst. The aim of this scoping review is to
systematically describe the use of ordinal outcomes in contemporary RCTs.
Specifically, we aim to (i) identify which target parameters are of interest in
trials that use an ordinal outcome; (ii) describe how ordinal outcomes are
analysed in RCTs to estimate a treatment effect; and (iii) describe whether
RCTs that use an ordinal outcome adequately report key methodological aspects
specific to the analysis of the outcome.
  Results from this review will outline the current state of practice of the
use of ordinal outcomes in RCTs. Ways to improve the analysis and reporting of
ordinal outcomes in RCTs will be discussed. We will review RCTs that are
published in the top four medical journals (BMJ, NEJM, The Lancet and JAMA)
between 1 January 2012 and 31 July 2022 that use an ordinal outcome. The review
will be conducted using PubMed. Our review will adhere to guidelines for
scoping reviews as described in the PRISMA-ScR checklist. The study
characteristics and design, including the target parameter(s) and statistical
methods will be extracted from eligible studies. The data will be summarised
using descriptive statistics.
