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 researched or a control treatment / placebo. See also double blind trial.
Chief Investigator (CI): the lead researcher/clinician who has overall responsibility for a clinical trial.
Clinical trial: a carefully designed and controlled study of a new intervention (e.g. a medicine, a physical activity-based treatment or a medical device), involving trial participants who have given informed consent to take part. A clinical trial will establish whether the new intervention is safe, whether it does what the researchers and doctors hope it will, whether there are any side effects, and how the intervention should be given (e.g. if it is a medicine, is it best swallowed as a tablet or taken as a nebulised medicine you inhale, how much and how often).
Comparative / controlled trial: a trial in which a new treatment being investigated for safety and effectiveness 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 new treatment being investigated.
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.
Informed consent: is when a person signs a consent form to confirm they are happy to take part in a particular clinical trial. When a person signs a consent form, they are also confirming that they have received all of the relevant information they need to make the decision to take part, and they clearly understand what taking part in the trial will involve.
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.
Lung clearance index (LCI): 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).
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.
Pharmacodynamics: the science or study of how the body reacts to a medication.
Pharmacokinetics: sometimes described as what the body does to a medication. It refers to the movement of that medication into, through, and out of the body - 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).
Pharmacovigilance study: an observational study which monitors the safety and effectiveness of a medication after it has been approved and licensed for use by the NHS, by evaluating on a larger scale the nature and prevalence of side effects and 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. These studies don't involve participants being asked to attend additional study visits or undergo additional investigations.
Phase: the different stages involved in the development of a new medication. Phase I / 1 focuses on initial safety in people. Phase II / 2 evaluates safety, correct dose and early signs of whether the medication works. Phase III / 3 is the stage before medication licensing and looks at the safety and effectiveness of a medication. Phase IV / 4 evaluates longer term use of a medication after it has been licensed.
Primary outcomes / endpoints: answers the most important questions about the trial, i.e. is the trial medication safe and effective?
Principal Investigator (PI): 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.
Real World Evidence (RWE) study: a study which looks at certain effects, usage, benefits or risks of a medication by gathering observational data in a real-world setting, e.g. clinical observations of a person who is taking the medication as part of their standard care, rather than as part of a clinical trial. People may be asked to complete questionnaires, keep a diary and / or go to the hospital to undergo additional investigations. RWE studies can help us understand the effects of a medication in a wider context and broader treatment population than a controlled clinical trial. They can also be important to help support regulatory decisions to approve or extend access to a medication through the NHS / other healthcare provider.
Recruitment target: the number of participants who need to be enrolled in the trial in the UK.
Sample size: the number of participants required to take part in a clinical trial to ensure enough data is collected to make the trial results meaningful.
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 which are of interest to the researchers, e.g. time to next pulmonary exacerbation. Like primary outcomes, the secondary outcome questions to be answered are decided upon during the trial design stage, before the trial begins.
Sponsor: 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).
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, i.e. exercise. Examples of CF study therapeutic categories include Anti-Infectives (e.g. medications to treat infections), Restore CFTR Function (e.g. for trials investigating the effectiveness of new CFTR modulator medications) and Genetic Therapies (e.g. treatments which target the genetic cause of CF).
Treatment arm: the group a participant is assigned to which determines the trial treatment regime they will receive, i.e. 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.