Explaining the jargon


What are…?

Explaining the jargon

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What it all means

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What are…?

A lot of the information you read about clinical trials can be quite complicated. This section of the website is to help you decipher some of the scientific jargon that is used to describe the designs of the trials and the processes involved.

What are eligibility criteria?

Eligibility criteria are standards or guidelines that outline who can and cannot participate in clinical trials.

Every trial has different criteria. These criteria are used by researchers to help them decide who may benefit from a new treatment and who can take part in the clinical trial. These are called inclusion criteria.

However, it is also important that a trial excludes people for whom the new treatment might not be safe or appropriate (exclusion criteria), such as pregnant women or those who are trying to get pregnant. Exclusion criteria are also based on things like age, gender, previous treatment history and other medical conditions.

What are randomised clinical trials?

To ensure the results of a clinical trial are correct, i.e. the results are due to treatment differences and not biased by known or unknown factors, researchers use randomised clinical trials.

Randomisation means that participants are randomly assigned to one or more treatment groups. This is carried out using a computer programme. Participants either receive the experimental treatment being investigated or are put into a control group. Those put into a control group are either given a standard treatment or a placebo.

Most trials split people into two groups and therefore the number of people receiving the experimental treatment is equal to the number of people in the control group. This means they are randomised 1:1. However, some trials split people into groups of three or four and this means they are randomised 2:1, or 3:1, etc.

What are placebo-controlled trials?

A placebo-controlled trial is a clinical trial where one group of participants are given a dummy treatment (a placebo).

A placebo is designed to be harmless and to have no effect. It looks smells and tastes like the treatment being tested, and participants may not know if they are on a placebo or the treatment itself. They can come in many forms: sugar-pills, creams, injections, drinks and even fake surgery.

Participants given a placebo usually make up the control group and are used to help investigators find out whether the treatment worked and that the improvements seen with the treatment are not due to a phenomenon called the placebo effect. The placebo effect refers to a person feeling better after taking a substance that has no known medicinal benefit. Placebos are commonly used in a blinded trial.

What are blinded vs. open label trials?

Blinded trial

If a trial is blinded, the participants of the trial do not know which treatment they are getting. Participants are also given identical looking injections or tablets, so they cannot tell which treatment they are having.

There is also the possibility of taking part in a double-blind trial. This is a trial where neither the participant nor the researchers know which treatment a participant is being given.

Open-label study

An open-label study means both you and your HCP know which type of treatment you are being given.



The removal of a small piece of tissue to enable detailed analysis in a laboratory.

Blinded trial

A trial in which the participants or researchers (if double-blind) do not know which treatment a participant is being given.

CT (computed tomography) scans

A scan that uses X-rays to give more detailed information of the inside of the body.


The quantity of a medicine or drug that is to be given at one time.

ECG (electrocardiogram)

A diagnostic tool that measures the electrical and muscular functions of the heart.

Eligibility criteria

Specific criteria that outline who can participate in clinical trials.

(European Medicines Agency)

The agency responsible for the scientific evaluation of medicines developed by pharmaceutical companies for use in the European Union.

Exclusion criteria

Specific criteria that exclude people from participating in a clinical trial.

(US Food and Drug Administration)

The agency that assures the safety, efficacy and security of human and veterinary drugs, biological products, medical devices, the nation’s food supply, cosmetics and products that emit radiation.


The period of time where clinical trial researchers keep track of the health of a participant after the trial ends.

Inclusion criteria

Specific criteria that a participant must meet or have to be included in the trial.

(Informed consent form)

A document that you sign to say you agree to participate in the clinical trial and understand what it may involve.

MRI (Magnetic Resonance Imaging) scans

Scans that use magnetic fields and radio waves to give more detailed information on the inside of the body.


A type of clinical trial in which both the researchers and participants know which treatment the participant is being given.

Palliative care

A type of care that aims to make patients, with an incurable illness, as comfortable as possible by controlling pain and other distressing symptoms. In addition, psychological, social and spiritual support is also offered to the patient and their family.

(Patient information sheet)

A document that you are given before joining a clinical trial that provides a summary of the clinical trial and explains your rights as a participant.


The different stages of a clinical trial. Each phase has a distinct purpose and helps researchers answer a variety of questions.


A dummy treatment that is designed to be harmless and to have no effect. It looks, smells and tastes like the treatment being tested, so that the participants do not know if they are on a placebo or the treatment itself.

Randomised clinical trials

A clinical trial in which the participants are randomly assigned to different treatments.


Removing consent for participation in a clinical trial. A patient’s consent can be withdrawn at any time.