Clinical trials glossary

A medical occurrence that may or may not have been caused by a trial treatment.

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

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

The lead researcher / clinician who has overall responsibility for a clinical trial.

A clinical trial is a type of research study. They investigate the effect of a treatment or ‘intervention’ on human health. 

A trial in which a new treatment is compared to an existing treatment. See our web page on types of clinical trial. 

The group of participants in a clinical trial that receives the control treatment (placebo or standard treatment), rather than the new treatment being investigated. See our web page on types of clinical trial. 

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

A clinical trial in which neither the participant nor the clinical / research team knows who is receiving the trial treatment and who is receiving the existing treatment or a placebo. See our web page on types of clinical trial. 

A treatment option that allows people with serious conditions to access medicines before they have been officially approved for use (also known as an expanded access programme).

The effectiveness of a treatment in achieving its intended purpose in a clinical trial.

The inclusion and exclusion criteria that determine 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 are a critical aspect of clinical trials. Before a trial can open, it must be given the necessary regulatory approval to open. Find out more about trial ethics.

Where someone has two copies of the same CF gene – for example two copies of F508del.

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

When a person signs a consent form to confirm they are happy to take part in a particular clinical trial. Find out more about being fully informed.

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

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

The lung clearance index, or LCI for short, measures how evenly air is distributed in the lungs and how well the lungs function. The air we breathe contains mostly oxygen and nitrogen. To measure LCI, the patient breathes normally while wearing a mask giving 100% oxygen. A machine measures how long it takes until the patient’s exhaled breath contains no more nitrogen (this takes up to 15 minutes depending on the patient’s health, and is repeated three times to get the best results).

Multiple ascending doses (MAD) can sometimes be used in early phase trials. People in a MAD trial are given the same treatment a number of times during the trial, with the dose given increasing throughout the trial. The aim of a MAD trial is to understand how the body tolerates and processes a new treatment at various doses.  See single ascending dose (SAD).

Multi-site trials are conducted at more than one CF centre.

A natural history study is a type of observational study. It monitors a group of people over time to see whether demographic, genetic, environmental and other factors affect the development of CF or certain outcomes. See our web page on types of clinical trial. 

A study where there is no intervention, but certain healthcare measures are observed and recorded over a period of time.It may collect new data or use data that has already been collected. See our web page on types of clinical trial. 

Unlike a blind trial, a clinical trial in which the researchers and the trial participants know they are taking the trial treatment. 

Normally occurs after a double blind trial. Participants are invited to enrol on an extension study which will involve taking the trial treatment for a period of time. No placebos are used in extension studies and both participant and researcher know the participant is taking the trial treatment.

The measurements or other assessments used to determine whether the trial treatment is safe and effective.

A dummy treatment, used to compare against a trial treatment. It has no medicinal effect.

The science or study of how the body reacts to a medication.

This is sometimes described as what the body does to a medication. It refers to the movement of a medication into, through, and out of the body. It looks at the process and time course of its absorption, bioavailability (the proportion of the medication that is available in the body to have its intended effect), distribution, metabolism (how it is broken down) and excretion (the removal of the medication and its broken-down components from the body).

An observational study that monitors the safety and effectiveness of a treatmentafter it has been approved and licensed for use by the NHS. It monitors the effects of a treatment, for example what kind of side effects people experience and how common they are, on a larger scale and evaluates the risks compared to its benefits. 

These studies inform doctors on how the medicines can be used, and also provide information on their cost effectiveness to healthcare providers. Participants are not asked to attend additional study visits or undergo additional investigations.

The different stages involved in the development of a new treatment. See our web page on phases of clinical trial.

These are the most important questions the trial is trying to answer, for example, whether the trial treatment safe and effective. See secondary outcomes. 

The researcher (clinician) who is responsible for a clinical trial at a particular trial site.

A scientific document that outlines the design of a clinical trial and how it will be conducted.

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. See our web page on types of clinical trial. 

A type of observational study that aims to find out the effects of a treatment outside of a clinical trial. It looks at certain effects, usage, benefits or risks of a treatment by gathering observational data in a real-world setting. See also our page on types of trial.

The number of participants who need to be enrolled in the trial in the UK.

The number of participants required to take part in a clinical trial to ensure enough data is collected to make the trial results meaningful.

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.

These answer other questions about the trial that are of interest to the researchers or that might help them to interpret the results of the primary outcomes. See primary outcomes.

Single ascending doses can be used in early phase trials. People in a single ascending dose (SAD) study are given one dose of the trial treatment. The aim of a SAD study is to understand how the body tolerates and processes a trial treatment. It usually precedes a multiple ascending dose study. See multiple ascending dose (MAD).

The individual, company, institution or organisation responsible for initiation, management, safety monitoring and financing of a clinical trial. Common sponsor types are academic sponsors (e.g. a university) and commercial sponsors (e.g. a pharmaceutical company).

The type of treatment or therapy being studied. For example, for a CF study, therapeutic areas include anti-infectives (medications to treat infections), treatments to restore CFTR function (such as new CFTR modulator medications) and genetic therapies. 

The group a participant is assigned to that determines the trial treatment regime they will receive, for example, the trial treatment or placebo. See our web page on types of clinical trial. 

The CF centre or other establishment at which the clinical trial takes place. Multi-site trials are conducted at more than one CF centre.