Welcome to the TwiCs network where we share information about Trials within Cohorts (TwiCs) system for designing and conducting practical randomised controlled trials.
Descriptive, ethical & US regulatory analysis of the TwiCs design "Ethics and practice of Trials within Cohorts" S Kim, J Flory, C Relton
PCTU, Queen Mary University, London
27th April 2019
MRC HTMR Trial Conduct Webinar
2nd International Symposium on Ethics of TwiCs (ppts and videos, and full published report)
Extension to Improve Reporting of Trials Using Observational Cohorts, Registries and Routinely Collected Health Data
(Funded by the Canadian Institutes of Health Research and the UK NIHR Clinical Trials Unit Support Funding)
The design (Trials within Cohorts)
Trials within Cohorts (TwiCs) embed one or more randomised controlled trials within cohorts.
The term 'TwiCs' was created for the first symposium on the 'cohort multiple RCT' design. This approach to trial design (the cmRCT design) was first described in the BMJ in 2010 article in the context of healthcare. Key features of the cmRCT design are:
(I) A large observational cohort of people with the condition
(II) Regular measurement of outcomes for the whole cohort
(III) Capacity for multiple randomised controlled trials over time
The advantages of the design are that the cohort serves as a representative
pool from which eligible people can be selected and approached for trial
participation and a platform in which multiple interventions
can be tested simultaneously (efficient use of control patients, improved
comparison between different interventions) and contamination between
study arms is minimised. As the design uses patient-centred informed
consent procedure this is expected to lead to higher, more representative
Since it's publication, more than 20 studies have started using the design in
systems to help address questions in a variety of fields (breast cancer,
bone metastases, rectal cancer, mental health, care of the elderly,
rare diseases, etc). The design is now being used to trial both
medicinal products (CTIMPs) and non-medicinal products.
Though originating in healthcare, the TwiCs approach to trial design can of course be used to inform decision making in any area, e.g. education, social care, crime, energy use.