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Use of the TwiCs design

Use of the TwiCs design is growing. Studies using the TwiCs design have obtained ethics board approval in: Australia, Brazil, Canada, China, Congo and Uganda, Denmark, Finland, France, Germany, India, Iran, Ireland Italy, Norway, Mexico, Netherlands, Spain, USA. Below are some examples of studies using the TwiCs approach.


Behavioural interventions for low back pain patients who are obese or overweight

This study aims to determine if a telephone based lifestyle behavioural intervention is effective in reducing pain intensity in overweight or obese patients with low back pain, compared to usual care. The study protocol was published here. The protocol for a causal mediation analysis of two trials in the project is here.


Optimising Brain Health in HIV

This study aims to provide a better understanding of the relationship between cognitive complaints, depression and HIV, and to facilitate trials of interventions to improve brain health in HIV. The protocol for the study can be found here. The trials nested within this cohort are registered as NCT02571504 and NCT02571595. For more information contact: Nancy E Mayo


FORBOW (Families Overcoming Risks and Building Opportunities)

This project  is recruiting the offspring of parents with severe mental illness including schizophrenia, bipolar disorder and severe depression. It aims to test multiple interventions to reduce the risk of developing mood or psychotic disorders. The study began recruiting young people at risk in Canada in 2013. The link to the published protocol can be found here. For more information contact Rudolf Uher.

The Cedar Project

An ongoing longitudinal cohort study addressing HIV and Hepatitis C vulnerability among young indigenous people who use drugs in Vancouver and Prince George, Brisith Columbia, Canada.The first trial use the cmRCT/ TwiCs approach is testing the impact of mHealth for HIV Prevention Among Young Indigenous People Who Use Illicit Drugs. The protocol for the trial (described as a multi-site Zelen pre-randomised trial) is published by BMC Central and the Clinical Trials registration can be found here.​

SPIN Scleroderma Patient-Centred Intervention Network

This CIHR funded study is recruiting an international cohort of people with the rare disease - scleroderma (Canada, France, USA, UK, France, Mexico) .  Over 1400 people have enrolled to date (August 2016). Four trials of interventions to help people manage this condition are ongoing. The protocol can be found here. Funding for two further trials was obtained in July 2016. For more information contact Brett Thombs

Collaborative Care for Diabetes and Ddepression

The Alberta's Caring for Diabetes (ABCD) Cohort Study is being used to test interventions for patients with diabetes and depression. The protocol for the TeamCare-PCN trial is here.



The Finnish Degenerative Meniscal Lesion Study (FIDELITY) This multi centre trial aims to determine whether arthroscopic partial meniscectomy of patients with degenerative meniscus injury is improved by a number of different types of surgery. For further information contact Teppo Jarvinen.


A group based in the Netherlands led by Helena Verkooijen have established ten hospital based cancer cohorts using the TwiCs approach including Breast, Rectal, Colorectal, Bone metastases, Lymph node metastases, Brain metastases, Prostate, Lung. 


The Utrecht cohort for Multiple BREast cancer intervention studies and Long-term evaLuAtion'. This study is based in the Department of Radiotherapy, University Medical Center in Utrecht, The Netherlands. The link to the study protocol can be found here. Email for more information. Here are the results of the latest trial embedded within this cohort . Hyperbaric Oxygen Therapy and Late Local Toxic Effects in Patients with Irradiated Breast Cancer: A randomised clinical trial. Mink van der Molen et al, 2024.  and an editorial by Hahn et al, 2024

PRESENT – Bone metastases

This ongoing study is based at the University Medical Centre in Untrech. The protocol for the first trial based in the cohort comparing conventional radiotherapy with stereotactic body radiotherapy in patients with spinal metastases can be found here. Email for more information.

Prospective National Colo-rectal Cancer Cohort - Website

This ongoing study is based in the University Medical Center, Utrecht, The Netherlands. The study started life as the ProspectIve data CollectioN Initiative on Colorectal cancer (PICNIC) study – a prospective observational cohort study. This study is now national and has changed its name and now has 59 participating centres throughout the Netherlands and almost 10,000 participants. The links to the study protocol can be found here. Email more information.​

United Kingdom


QIST (Quality Improvement for Surgical Teams) Collaborative - A collaborative, longitudinal observational cohort study (Arthroplasty Research Cohort) of 5000+ patients undergoing primary hip and knee replacement in the United Kingdom. For more information contact


BLADDER CANCER - Graham Roberts Study protocol: first ‘trials within cohort study’ for bladder cancer

For more information contact

RENAL CANCER  - Nephron-sparing treatment for small renal masses -

For more information contact


This is a prospective, observational cohort study aiming to collect information on 700 patients diagnosed with mesothelioma over the next ten years.  This will provide a much-needed picture of the natural history of the disease, as well as symptom course and outcomes.  The study is sites across the UK.  ASSESS-meso is funded by the Avon Mesothelioma Foundation. Within ASSESS-meso, we have designed TILT – a Trial of Intra-pleural bacteriaL immunoTherapy, using the TwiC approach.  This is an NIHR-funded feasibility study of a novel treatment, with embedded qualitative interviews to explore participants' experiences.  Recruitment opened 2017. For information on either study, please Anna Bibby.


The COVIDENCE UK Research Study was launched in May 2020 in response to the outbreak of coronavirus disease (COVID-19). A total of 19981 participants enrolled and consented to 5-year follow-up with medical record linkage. This population based cohort study has the capacity to support trial-within-cohort studies to evaluate interventions for prevention of COVID-19 and other acute respiratory illnesses. The first COVIDENCE trial 'CORONAVIT'  was launched in October 2020. 

Cystic Fibrosis Healthhub Data Observatory

This UK (NIHR funded) quality improvement project and Trials within Cohorts platform for Cystic Fibrosis (CF) aims to recruit 6,000 adults with CF to help research projects including trials of interventions for CF. Email for more information. The protocol and PIS are available here.

Yorkshire Health Study

Ongoing population based regional cohort aiming to improve long term health of the region. Recruitment initally through GP practices in South Yorkshire, then widened to the Yorkshire region. Two waves of data collection (2010-2012, and 2013-2015), further waves planned. 22 studies have recruited through the cohort including several trials (DEPSY)

For more information contact Clare Relton.


This pragmatic trial using the ‘cohort multiple randomised controlled trial’ design tested the effectiveness of adjunctive treatment by homeopaths compared to usual care alone, over a period of twelve months in 577 patients with self-reported depression. This is the first published completed trial using the cmRCT design (link). To read about the benefits and challenges experienced in the use of this trial design see the link to this article published in the journal Trials

Menopausal Hot Flush Study

This was the first (partial) pilot of the cmRCT design. A small cohort of women with severe/ frequent menopausal hot flushes were recruited to the observational study and one RCT conducted testing the effectiveness of the offer of a course of treatment by a homeopath compared to no offer. The trial was published in Contemporary Clinical Trials..

For more information contact Clare Relton.


CLASSIC (Comprehensive Longitudinal Assessment of Salford Integrated Care) study

This NIHR funded study tested the implementation and effectiveness of new models of care for people with long term conditions. The cohort of 4,000 was recruited through GP practices in  the Salford area of the UK. The study protocol can be found here. For more information please contact Peter Bower.

BIBBS (Born in Bradford Better Start Study)

An experimental birth cohort study designed to evaluate the impact of early life interventions. The cohort plans to recruit 5,000 babies and their mothers and mother's partners over five years by 2020 and test a number of interventions to improve health and social outcomes during the critical early years. For more information contact Josie Dickerson.

CARE (The Yorkshire & Humber Community Ageing Research Study)

This cohort is recruiting 1,000 patients over 75 years registered with GP practices in the Yorkshire & Humber area of the UK. The researchers plan to trial interventions to improve health and wellbeing in this population. This study is funded by the NIHR CLAHRC YH. The study is registered here and the study website is here. For more information contact: Andrew Clegg or Anne Heaven.


This cohort was initially formed in order to conduct a cmRCT of a multifaceted podiatry intervention for the prevention of falls in older people. The study originally recruited 2,600 people from routine podiatry clinics to the REFORM cohort. During 2016-17, this cohort is being utilised to test a second intervention to prevent falls in the elderly – details of which can be found here. The link to the original REFORM cohort study and trial protocol is here. The study is led by David Torgerson at York University in the UK. The results of this trial are now published.

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