Your donation will make a difference:
Cystic Fibrosis Trust

Clinical trials glossary

Explore our glossary to find out more about some common terms you may hear relating to cystic fibrosis clinical trials.


Adverse event: a medical occurrence which may or may not have been caused by a trial medication.

Adverse reaction: an unfavourable and unintended side-effect experienced by a clinical trial participant which is directly related to the treatment being administered.

Blind trial: a clinical trial in which the participants do not know whether they are receiving the intervention being tested or a control treatment/ placebo. See also double blind trial.

Chief Investigator: the lead researcher/clinician who has overall responsibility for a clinical trial.

Comparative / controlled trial: a trial in which an investigational treatment is compared to an existing treatment.

Compassionate use scheme: a treatment option that allows medicines to be accessed by seriously ill patients, before they have been officially approved for use (also known as an expanded access programme).

Control group: the group of participants in a clinical trial that receives the control treatment (placebo or standard treatment), rather than the investigational treatment.

Data: clinical information about the safety and effectiveness of treatments in a clinical trial.

Double blind trial: a clinical trial in which neither the participant nor the clinical/research team knows who is receiving the trial medication and who is receiving the existing treatment or a placebo.

Efficacy: the effectiveness of a treatment in achieving its intended purpose.

Eligibility criteria: the inclusion and exclusion criteria which determines who can take part in the trial. These criteria are based on factors such as age, CF genotype, previous treatment history, and existence of other medical conditions.

Ethics: ethics are a critical aspect of clinical trials, and a key concern for research involving humans and animals. Before a trial is given the necessary regulatory approval to open, regulatory bodies will seek to ensure that the trial is conducted by qualified researchers and has a valid purpose, that participants will be fully informed as to what the trial will involve, and that the trial will not cause undue harm to participants.

Homozygous - where someone has two copies of the same CF gene – for example two copies of F508del.

Heterozygous - where someone has two variations of the CF gene – for example, one copy of F508del and one other variation such as G551D or R117H.

Intervention: a treatment (medication or other) being investigated in a clinical trial.

Length of participation: the length of time a participant will take part in a trial, from the first to the last appointment.

Observational study: a study where there is no intervention, but certain healthcare measures are observed and recorded over a period of time.

Open-label trial: unlike a blind trial, a clinical trial in which the researchers and the trial participants know they are taking the trial medication.

Open-label extension: normally occurs after a double blind trial; participants are invited to enrol on an extension study which will involve taking the trial medication for a period of time. No placebos are used in extension studies and both participant and researcher know the participant is taking the trial medication.

Outcome measures: the measurements or other assessments used to determine whether the trial medication is safe and effective.

Placebo: a dummy medication, used to compare against a trial medication. It has no medicinal effect.

Phase: the different stages involved in the development of a new medication. Phase I focuses on initial safety in people. Phase 2 evaluates safety, correct dose and early signs of whether the medication works. Phase 3 is the stage before medication licensing and looks at safety and medication efficacy. Phase 4 evaluates longer term use of a medication after it has been licensed.

Primary outcomes: answers the most important questions about the trial, ie is the trial medication safe and effective?

Principal Investigator: the researcher (clinician) who is responsible for a clinical trial at a particular trial site.

Protocol: a scientific document which outlines the design of a clinical trial and how it will be conducted.

Randomised controlled trial (RCT): a trial in which participants are randomly assigned to one of two or more treatment arms of a clinical trial (see ‘treatment arm’). This is usually done by computer, so that each group has a similar mix of people of different ages, sexes and states of health.

Recruitment target: the number of participants who need to be recruited for the trial in the UK.

Sample size: the number of participants in a clinical trial.

Screening: the first official assessment for a participant in a trial, where it is checked if the participant meets all of the inclusion and exclusion criteria.

Secondary outcomes: answers other questions about the trial e.g. time to next pulmonary exacerbation.

Sponsor: the individual, company, institution or organisation responsible for initiation, management, safety monitoring and financing of a clinical trial.

Therapeutic category: the type of treatment or therapy being studied. A therapy could range from a medication addressing a particular characteristic of CF to a device or activity, ie exercise.

Treatment arm: the group a participant is assigned to which determines the trial treatment regime they will receive, ie the trial medication or placebo.

Trial site: the CF centre or other establishment at which the clinical trial takes place – multi-site trials are conducted at more than one CF centre.


Clinical Trials Digital Hub

We've got everything you might want to know about clinical trials on our Clinical Trials Digital Hub, including resources, information about taking part and more!

Explore

Meet the team

There are a number of different professionals involved in making sure clinical trials are as successful as possible.

Find out more

Trials for young people

Take a look at the resources available for young people involved in clinical trials.

Tell me more