Subgroup analyses in randomised controlled trials frequently categorised continuous subgroup information

Williamson, S. Faye, Grayling, Michael J., Mander, Adrian P. ORCID: https://orcid.org/0000-0002-0742-9040, Noor, Nurulamin M., Savage, Joshua S., Yap, Christina and Wason, James M.S. 2022. Subgroup analyses in randomised controlled trials frequently categorised continuous subgroup information. Journal of Clinical Epidemiology 150 , pp. 72-79. 10.1016/j.jclinepi.2022.06.017

Preview

PDF - Published Version Available under License Creative Commons Attribution. Download (500kB) | Preview

Abstract

Objective To investigate how subgroup analyses of published Randomised Controlled Trials (RCTs) are performed when subgroups are created from continuous variables. Study design and setting We carried out a review of RCTs published in 2016–2021 that included subgroup analyses. Information was extracted on whether any of the subgroups were based on continuous variables and, if so, how they were analysed. Results Out of 428 reviewed papers, 258 (60.4%) reported RCTs with a subgroup analysis. Of these, 178/258 (69%) had at least one subgroup formed from a continuous variable and 14/258 (5.4%) were unclear. The vast majority (169/178, 94.9%) dichotomised the continuous variable and treated the subgroup as categorical. The most common way of dichotomising was using a pre-specified cutpoint (129/169, 76.3%), followed by a data-driven cutpoint (26/169, 15.4%), such as the median. Conclusion It is common for subgroup analyses to use continuous variables to define subgroups. The vast majority dichotomise the continuous variable and, consequently, may lose substantial amounts of statistical information (equivalent to reducing the sample size by at least a third). More advanced methods that can improve efficiency, through optimally choosing cutpoints or directly using the continuous information, are rarely used.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine Centre for Trials Research (CNTRR)
Additional Information:	License information from Publisher: LICENSE 1: URL: http://creativecommons.org/licenses/by/4.0/, Start Date: 2022-06-30
Publisher:	Elsevier
ISSN:	0895-4356
Date of First Compliant Deposit:	7 July 2022
Date of Acceptance:	28 June 2022
Last Modified:	09 May 2023 17:32
URI:	https://orca.cardiff.ac.uk/id/eprint/151084

Citation Data

Cited 1 time in Scopus. View in Scopus. Powered By Scopus® Data

Actions (repository staff only)

Edit Item