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What are clinical trials?

Clinical trials are a type of medical research carried out to test new drugs, vaccines, medical devices, procedures or ways of organising care.

These trials may be carried out in NHS hospitals or clinics, and may be run by parts of the NHS, drug companies, research institutes or universities.

Funding for research may come from private companies, the NHS, the Medical Research Council or health charities. Trials may include patients with existing conditions, people in the community or healthy volunteers.

A trial for a new drug may compare how effective it is against an existing treatment, or against a dummy treatment called a placebo. Those receiving the placebo are known as the control group. Often people respond well to the fake treatment, even though it has no active medical components. This is called the placebo effect.

For trials to give the best results, no one involved should know which participants are having the active treatment, such as a drug, and which are getting a placebo. This is known as a double blind trial. 'Double' because neither the researchers nor the patients know who has been assigned to which group. To be sure that the results are not influenced by other factors, patients are assigned to the active or control groups at random. This is done using special randomising techniques and should ensure there's less room for bias in the results.


Regulating clinical trials

Medical research trials in the UK are strictly regulated to ensure the safety of people taking part, and to improve the accuracy of the findings. The Medicines and Healthcare products Regulatory Agency (MHRA) has to give a special authorisation before trials of medicines can begin to make sure protocols are followed.

Other health research may involve looking for links between some conditions, activities or drugs and different outcomes. For example, groups of people may be studied to see whether taking more exercise reduces their risk of developing conditions like heart disease. In a clinical trial, different groups would be allocated to different circumstances, such as to exercise more or not, and would be followed to see what happens to them.

There are other types of research that look at people's existing circumstances to try to see whether it has made a difference, for example, whether people who exercise more are less likely to develop heart disease. These 'observational studies' are not clinical trials so cannot always be used to make a clear cause-and-effect conclusion. As in all medical research, the results may be influenced by many factors, including where people live, their age, their social circumstances, such as how well-off they are, and their lifestyle, such as whether or not they smoke. Such factors may also affect participants in clinical trials, but the researchers may try to allow for this in the way they are selected, for example, by making sure that the active and control groups have similar age ranges.

There are many other factors that can affect the results of medical research. For example, if a study involves people completing questionnaires, this can also affect findings if they give inaccurate answers, for example about their sexual behaviour or how much alcohol they drink.

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