Simple randomisation
Randomization without restriction. In a two-group trial, it is analogous to the toss of a coin.
Block randomisation
Block randomisation allows the trial investigators to control the numbers of subjects allocated to each group during the enrollment phase of the study by using blocks of sequences of allocation assignment, wherein each letter represents an intervention or arm of the trial, (e.g. blocks of four might consist of: AABB, ABAB, ABBA, etc). This example shows an equal distribution of participants to each arm of the study but this might not always be the case.
The blocks can be of any size, but ideally the size should correspond to a multiple of the number of groups in the study. (Altman DG. Practical statistics for medical research. London: Chapman & Hall, 1991.)
Stratified block randomisation
Stratified block randomisation can further restrict chance imbalances to ensure the treatment groups are as alike as possible for selected prognostic variables or other patient factors. A set of permuted blocks is generated for each combination of prognostic factors. This ensures that treatments are balanced at the end of every strata block.
Minimisation
Minimisation is used as an alternative method to stratified randomisation to provide treatment groups that are similar for several variables. Stratified randomisation on several variables can lead to large numbers of strata. This can lead to a large number of incomplete blocks and to a substantial imbalance overall which minimisation can avoid.
The principle behind minimisation:
People are allocated (with a probability greater than 50%) to the treatment group that would minimise the imbalance between the groups with respect to the variables of interest.
Criteria for method:
This method depends on the characteristics of the person entering the trial (the first person is entered by simple randomisation) and therefore no pre-arranged list can be constructed.
Example:
Suppose that 20 people have been entered into the trial in this centre and that the next person that is ready to receive the treatment assignment is <10, male and <2 years since diagnosis. A table can be constructed as follows for a similar table/explanation:
Characteristic | Grouping | Active | Placebo |
---|---|---|---|
Age | <10 10-14 14+ | 4 2 4 | 4 3 3 |
Sex | Male Female | 7 3 | 6 4 |
Time since diagnosis | < 2 Years 2 Years + | 6 4 | 5 5 |
The treatment allocation for this person is determined by looking at the number of people already in the study with these characteristics by treatment group, i.e.
<10 | Male | <2 Years | Total | |
---|---|---|---|---|
Active | 4 | 7 | 6 | 17 |
Placebo | 4 | 6 | 5 | 15 |
Therefore to make the groups as similar as possible allocate this person (with probability > 1/2) to the placebo group.
The NIHR Research Support Service – RSS – is a national service providing support and advice to researchers based in England developing funding applications at all stages of the research pathway, from pre award to post award and delivery.
The CRFs at Guy’s Hospital, St Thomas’ Hospital and King’s College Hospital provide welcoming, comfortable, and safe environments in which patients and volunteers can participate in clinical studies.
https://www.maudsleybrc.nihr.ac.uk/nihr-wellcome-kings-clinical-research-facility
www.guysandstthomasbrc.nihr.ac.uk/Professionals/Corefacilities/Clinicalresearchfacility/Clinicalresearchfacilities.aspx
The KHP-CTO is based at Guy’s Campus and contracted as a function of the NHS R&D departments (South London and Maudsley NHS Trust (SLaM), Guy’s and St Thomas’ NHS Trust (GSTT) and King’s College Hospital (KCH)) and King’s College London (KCL) to support CTIMPs. In relation to academic trials, the scope of the KHP-CTO quality team is to support investigators at King’s Health Partners institutions who undertake CTIMP clinical trials where King’s Health Partners are sponsor or co-sponsor to ensure delivery of the statutory obligations contingent on sponsorship of trials.
www.khpcto.co.uk
Researchers wishing to conduct research in the NHS (or Health and Social Care (HSC) in Northern Ireland) must obtain NHS or HSC management permission (also referred to as R&D approval) for each NHS/HSC research site. If your research involves undertaking the research on the premises of a NHS organisation, with NHS patients or with NHS staff, then you should contact the local NHS R&D office.
SLaM www.kcl.ac.uk/ioppn/research/office/index.aspx
KCH www.kch.nhs.uk/research/setting-up/contact-research-office
GSTT www.guysandstthomas.nhs.uk/research/researchers/registering-research.aspx
The Research Grants & Contracts Department (RG&C) deals with all administrative, financial and legal aspects of externally funded research in the College. RG&C also negotiates agreements which underpin or facilitate academic research taking place.
https://www.kcl.ac.uk/research/support/applications/index
These are UK-wide regional centres of excellence that will undertake high-quality research into clinical trial methodology. The methodology hubs will have close links with those carrying out clinical trials. Individual hubs will offer specific clinical and methodological expertise.
www.methodologyhubs.mrc.ac.uk/
We at the KCTU do not directly get involved in recruitment to trials. However, the following links are large databases which allow you to search for trials both in the United Kingdom and around the world based on keywords:
http://www.isrctn.org
http://clinicaltrials.gov
https://bepartofresearch.nihr.ac.uk/taking-part/
If your study is in the area of mental health or neurosciences, please make an appointment initially to speak to an NIHR RSS advisor at www.ctu.co.uk/NIHR-RSS
For all other clinical areas, a brief support request form must be submitted.
We strongly advise that researchers approach KCTU at the grant application stage, ideally 3-4 months in advance of the submission deadline to get the best possible input and consideration.
Requests for support are circulated to the relevant senior academic and operational staff for consideration, to ensure that the best possible match between the trial and the expert collaborator is achieved.
020 7848 0532 | ctu@kcl.ac.uk
Clinical Trials Unit
King’s College London PO64, Room M2.06,
Institute of Psychiatry, 16 De Crespigny Park,
London, SE5 8AF
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