Welcome to the TwiCs network where we share  information about the Trials within Cohorts (TwiCs) system for designing and conducting practical randomised controlled trials.
The first COVID study using the TwiCs design has been launched.
COVIDENCE UK Research Study has been developed in response to the outbreak of coronavirus disease (COVID-19).
This study plans to recruit a population based cohort of 12,000+ adults. This will then provide a platform for multiple trials of interventions to prevent COVID related disease and improve health 
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): an approach to trial design which uses infrastructures (cohorts) to facilitate multiple randomised controlled trials

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


More than 70 studies have or are using the design. Researchers in 

the UK, Canada, USA, France, Netherlands, Finland, and Australia;  are use

the TwiCs design approach 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 be used to inform decision making in any area, e.g. education, social care, crime, energy use.  

This website describes key features of the TwiCs approach and links to articles describing the methodologies, and examples of use of the TwiCs

approach in hospital settings and primary care/ population based settings

© 2018 Trials within Cohorts    Contact: c.relton@qmul.ac.uk.  Supported  by  Wellcome Trust grant and the NIHR CLAHRC for Yorkshire & Humber