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Abstract
A brief summary of the study and its results.
Adverse Event
Any unfavourable and unintended signs, including abnormal laboratory results, symptoms or a disease associated with treatment.
Adverse Reactions
These are adverse events but causally related to investigational medicinal products.
Arm
Refers to a group of participants allocated to a particular treatment. In a randomised controlled trial, allocation to different arms is determined by the randomisation procedure. Many controlled trials have two arms, a group of participants assigned to an experimental intervention (sometimes called the treatment arm) and a group of participants assigned to a control (the control arm). Trials may have more than two arms.
Attrition
The loss of participants during the course of a study. Also called ‘loss to follow up’.
Bias
A systematic error or deviation in results or inferences from the truth. In studies of the effects of health care, the main types of bias arise from systematic differences in the groups that are compared (selection bias), the care that is provided, exposure to other factors apart from the intervention of interest (performance bias), withdrawals or exclusions of people entered into a study (attrition bias) or how outcomes are assessed (detection bias). Reviews of studies may also be affected by reporting bias, where a biased subset of all the relevant data is available.
Blinding
The process of preventing those involved in a trial from knowing which comparison group a participant belongs to. The risk of bias is minimised when fewer people know who is receiving the experimental intervention or the control intervention. Participants, caregivers, outcome assessors, and analysts are all candidates for being blinded. Blinding of certain groups is not always possible, for example, surgeons in surgical trials.
Case Report Form (CRF)
A paper or electronic questionnaire specifically used in clinical trial research. This form is the tool used by the sponsor of the clinical trial to collect data from each participating patient. All data on each patient participating in a clinical trial are held and/or documented in the CRF, including adverse events.
Chief Investigator (CI)
An individual who is responsible for the conduct of the whole project in the UK.
Clinical Trial
An experiment to compare the effects of two or more healthcare interventions. ‘Clinical trial’ is an umbrella term for a variety of healthcare trial designs.
Clinical Trial of an Investigational Medicinal Product (CTIMP)
Clinical Trial of an Investigational Medicinal Product is a study that looks at the safety or efficacy of a medicine/foodstuff/placebo in human.
Cluster Randomised Trial
A trial where clusters of individuals (e.g. clinics, families, geographical areas), rather than individuals themselves, are randomised to different arms.
Cohort Study
An observational study in which a defined group of people (the cohort) is followed over time. The outcomes of people in subsets of this cohort are compared, to examine people who were exposed or not exposed (or exposed at different levels) to a particular intervention or other factor of interest. A prospective cohort study assembles participants and follows them into the future. A retrospective (or historical) cohort study identifies subjects from past records and follows them from the time of those records to the present.
Confidence interval
A measure of the uncertainty around the main finding of a statistical analysis. Wider intervals indicate lower precision and narrow intervals indicate greater precision.
Confounders
Factors that are associated with both an intervention and the outcome of interest. For example, if people in the experimental group of a controlled trial are younger than those in the control group, it will be difficult to decide whether a lower risk of death in one group is due to the intervention or the difference in age. Age is then said to be a confounder, or a confounding variable. Randomisation is used to minimise imbalances in confounding variables between experimental and control groups. Confounding is a major concern in non-randomised trials.
Control
A participant in the arm that acts as a comparator for one or more experimental interventions. Controls may receive placebo, no treatment, standard treatment, or an active intervention, such as a standard drug.
Cost Effectiveness Analysis
An economic analysis that views effects in terms of overall health specific to the problem, and describes the costs for some additional health gain (e.g. cost per additional stroke prevented).
Diagnostic Test
A diagnostic test is an indicator or predictor of an illness state. As such, the term needs to be interpreted broadly as it includes diagnostic tests, screening, tests to stage disease, treatment monitoring, and estimate prognosis estimation.
Efficacy
The extent to which an intervention produces a beneficial result under ideal conditions. Clinical trials that assess efficacy are sometimes called explanatory trials.
Epidemiology
The study of population and community health, not just individuals.
Factorial Design
A trial design used to assess the individual contribution of treatments given in combination, as well as any interactive effect they may have. In a trial using a 2×2 factorial design, participants are allocated to one of four possible combinations. This type of study is usually carried out in circumstances where no interaction is likely.
Feasibility Study
Feasibility Studies are pieces of research done before a main study in order to answer the question “Can this study be done?”. They are used to estimate important parameters that are needed to design the main study.
Follow Up
The observation over a period of study/trial participants to measure outcomes under investigation.
Good Clinical Practice (GCP)
The international ethical, scientific and practical standard to which all clinical research is conducted.
Good Manufacturing Practice (GMP)
The minimum standard that a medicines manufacturer must meet in their production processes. The European Medicines Agency (EMA) coordinates inspections to verify compliance with these standards and plays a key role in harmonising GMP activities at European Union (EU) level.
Interaction
The situation in which the effect of one independent variable on the outcome is affected by the value of a second independent variable.
Interim Analysis
Analysis comparing intervention groups at any time before the formal completion of a trial, usually before recruitment is complete. Often used with stopping rules so that a trial can be stopped if participants are being put at risk unnecessarily. Timing and frequency of interim analyses should be specified in the protocol.
Intervention
The process of intervening on people, groups, entities or objects in an experimental study. In controlled trials, the word is sometimes used to describe the regimens in all comparison groups, including placebo and no-treatment arms.
Investigator Site File
For every research study it is important to keep clear accurate version controls of all trial related documents.
Meta Analysis
Combining data from multiple independent studies.
Monitoring
Maintaining contact with funded projects to ensure they progress satisfactorily and deliver meaningful results.
Morbidity
Illness or harm.
Multicentre Trial
A trial conducted at several geographical sites. Trials are sometimes conducted among several collaborating institutions, rather than at a single institution – particularly when large numbers of participants are needed.
Non-inferiority Trial
A trial designed to determine whether the effect of a new treatment is not worse than a standard treatment by more than a pre-specified amount.
Observational Study
An observational study in which a defined group of people (the cohort) is followed over time. The outcomes of people in subsets of this cohort are compared, to examine people who were exposed or not exposed (or exposed at different levels) to a particular intervention or other factor of interest. A prospective cohort study assembles participants and follows them into the future. A retrospective (or historical) cohort study identifies subjects from past records and follows them from the time of those records to the present.
Outcome
A component of a participant’s clinical and functional status after an intervention has been applied, that is used to assess the effectiveness of an intervention.
Output
Published results from a research project. NIHR projects often generate papers that are published in the scientific literature. Full details of NIHR projects and their results are published in special reports or journals.
Participant
An individual who is studied in a trial, often, but not necessarily, a patient.
Patient and Public involvement (PPI)
Actively working in partnership with patients and members of the public to plan, manage, design and carry out research.
Patient Information Leaflet (PIL)
Provides information to patients to encourage participation in their health care.
Peer Review
A reviewing process for checking the quality and importance of reports of research. An article submitted for publication in a peer-reviewed journal is reviewed by other experts in the area.
Phases
Phase I = first in human
Phase II = proof of concept/efficacy
Phases III-V = effectiveness
Pilot Studies
Pilot studies are a smaller version of the main study used to test whether the components of the main study can all work together. It is focused on the processes of the main study, for example to ensure that recruitment, randomisation, treatment, and follow-up assessments all run smoothly.
Placebo
An inactive substance or procedure administered to a participant, usually to compare its effects with those of a real drug or other intervention, but sometimes for the psychological benefit of the belief of receiving treatment. Placebos are used in clinical trials to blind people to their treatment allocation. Placebos should be indistinguishable from the active intervention to ensure adequate blinding.
Power
The probability of rejecting the null hypothesis when a specific alternative hypothesis is true. In clinical trials, power is the probability that a trial will detect, as statistically significant, an intervention effect of a specified size. Ideally, we want a test to have high power.
Pragmatic Trial
A trial that aims to test a treatment policy in a ‘real life’ situation, when many people may not receive all of the treatment and may use other treatments as well.
Primary Outcome
The outcome of greatest importance.
Primary Research
Experimental studies generating new data (cf. secondary research, which analyses existing data).
Principal Investigator (PI)
An individual responsible for the conduct of the research at a research site. There should be one PI for each research site. In the case of a single-site study, the chief investigator and the PI will normally be the same person.
Probability
The chance or risk of something happening.
Protocol
The plan or set of steps to be followed in a study.
Randomisation
This is when a trial participant has the same chance of being allocated to each type of treatment being compared, but the allocation is decided at random by a computer
Randomised Controlled Trial (RCT)
An experiment in which two or more interventions, possibly including a control intervention or no intervention, are compared by being randomly allocated to participants. In most trials one intervention is assigned to each individual but sometimes assignment is to defined groups of individuals (for example, in a household) or interventions are assigned within individuals (for example, in different orders or to different parts of the body).
Retrospective Study
A study in which the outcomes have occurred before the study commenced. Case-control studies and cohort studies can be retrospective, but randomised controlled trials never are.
Secondary Outcome
An outcome used to evaluate additional effects of an intervention deemed as being less important than the primary outcomes.
Secondary Research
A review of individual studies (each of which is called a primary study). A systematic review is a secondary study.
Serious Adverse Device Effect (SADE)
An SAE that occurs during research with a medical device may be a SADE.
Serious Adverse Event (SAE)
Any events suspected to be caused by an Investigational Medicinal Product (IMP), but which are not consistent with information about the IMP (these are the most serious of events and are subject to expedited reporting procedures).
Site Initiation Visit (SIV)
A visit to prepare and set up a research site to conduct a study and must occur prior to patient recruitment.
Specificity
In screening / diagnostic tests this is a measure of a test’s ability to correctly identify people who do not have the disease.
Standard Operating Procedure (SOP)
Written procedures, with detailed instructions to record routine operations, processes and practices followed within a research trial/unit.
Statistically Significant
A result that is unlikely to have happened by chance.
Suspected Unexpected Serious Adverse Reaction (SUSAR)
A reaction to the study treatment where the nature and severity are not consistent with the information about the medicinal product.
Systematic Review
A review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyse and summarise the results of the included studies.
Treatment
The process of intervening with the aim of enhancing health or life expectancy. Sometimes, and particularly in statistical texts, the word is used to cover all comparison groups, including placebo and no treatment arms of a controlled trial and even interventions designed to prevent bad outcomes in healthy people, rather than cure ill people.
Trial Master File (TMF)
A collection of essential documents which allows the conduct of a clinical trial to be reconstructed and evaluated.