Pragmatic Clinical Trials Unit

Courses and Events menu

Introduction to Trials within Cohorts (TwiCs)


Studies using the ‘Trials within Cohorts’ (TwiCs) approach (Relton et al, 2010) enable researchers to embed multiple randomised trials (with usual care comparators) within a researcher or routine health generated cohort.

TwiCs studies collect data on the exposures and outcomes of a group of patients (i.e. cohort). This provides a platform for research, including multiple randomised trials with usual care comparators. Those joining the cohort initially grant permission for their data to be used for intervention research. For each succeeding randomised trial, a proportion of those eligible are randomly selected to be offered the intervention, and their outcomes compared to those eligible patients not offered the intervention (these may be new interventions or interventions already being routinely delivered). Patients randomised to this offer group are told (after randomisation) that they have been randomly selected, and a secondary consent, clinical in character, is obtained to receive the intervention. In most studies using the TwiCs approach, cohort patients explicitly consent to not know at a future date if they have been randomised to usual care. 

There are a growing number of funded and ethics board approved studies using the TwiCs approach both in the UK and internationally in a wide range of clinical areas (e.g. cancer, osteoarthritis, rare diseases, severe mental illness, depression, dementia, ADHD). Some clinical areas are recommending this approach for trials assessing interventions to inform future policy and practice (e.g. Psychological therapies, Holmes et al, 2018). CONSORT Guidelines for the reporting of this approach are currently being developed. 

Course Details


 Senior Lecturer in Clinical Trials

Pragmatic Clinical Trials Unit

 Queen Mary University, London

  • Petter Viksveen

 Post Doctoral Researcher

 University of Stavanger, Norway 

Who this course is for

Anyone involved in the design, conduct, analysis or reporting of pragmatic trials in the academic or NHS sector. The course will be of interest to all triallists, including principal investigators, trial managers, early career researchers and PhD students

Course content

This practical one-day course will provide participants with an understanding of the key features of the TwiCs approach to pragmatic trial design. 

The day will include information and guidance on how to plan studies using this approach, how to analyse TwiCs trials, different ways to approach informed consent, how to obtain HRA and MHRA approvals, and how to report TwiCs trials.

Course participants will be provided with a wide range of examples of UK and international studies using the TwiCs approach (e.g. mental health, cancer, musculoskeletal diseases).

We will discuss the strengths and weaknesses of the TwiCs approach compared to the standard approach to pragmatic trial design and other innovative approaches to trial design which also leverage existing databases for trials (e.g. randomised registry trials, electronic health record/ point-of-care trials, administrative trials and platform trials.)

Please note that this event has already taken place.

For more information about other PCTU courses, please contact PCTU Administrator.

Return to top