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A carer is a relative, friend or partner who provides, intends to provide, or used to provide a substantial amount of care to another person on a regular basis, but not necessarily through living with them.

    Chief investigator

    The chief investigator (CI) is the person who takes overall responsibility for the design, conduct and reporting of a study.


      The CLAHRCs (Collaborations for Leadership in Applied Health Research and Care) were superseded by the 15 NIHR Applied Research Collaborations (ARCs) in 2019.

        Clinical guideline

        A systematically developed statement for practitioners and participants about appropriate health care for specific clinical circumstances.

          Clinical research

          Clinical research aims to find out the causes of human illness and how it can be treated or prevented. This type of research is based on examining and observing people with different conditions and sometimes comparing them with healthy people. It can also involve research on samples of blood or other tissues, or tests such as scans or X-rays. Clinical researchers will also sometimes analyse the information in patient records, or the data from health and lifestyle surveys.

            Clinical Research Facilities

            NIHR’s 23 Clinical Research Facilities (CRFs) are purpose built facilities in NHS hospitals where researchers can deliver early-phase and complex studies.

              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 authorisation

                Authorisation by a competent authority (Medicines and Healthcare products Regulatory Agency in the UK) to conduct a clinical trial.

                  Clinical trials units

                  Specialist units with a specific remit to design, conduct, analyse and publish clinical trials and other well-designed studies. The NIHR provides support funding for a number of UKCRC registered units.


                    An online archive of scholarly materials.

                      Cluster randomised trial

                      A trial where clusters of individuals (e.g. clinics, families, geographical areas), rather than individuals themselves, are randomised to different arms.

                        Cochrane collaboration

                        The Cochrane Collaboration is an international, non-profit, independent organisation. It ensures that up-to-date and accurate information about the effects of healthcare interventions is readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions, and promotes the search for evidence in the form of clinical trials and other studies on the effects of interventions.

                          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.


                            Collaboration involves active, on-going partnership with members of the public in the research process. For example, members of the public might take part in an advisory group for a research project, or collaborate with researchers to design, undertake and/or disseminate the results of a research project.

                              Commissioned call

                              Calls for proposals based on pre-defined research questions developed to respond to the information needs of decision-makers (typically, but not exclusively, within the NHS).

                                Commissioned workstreams

                                Commissioned workstreams start with the information needs of decision makers typically, but not exclusively, within the NHS. These are refined and prioritised by experts in the field, and commissioning briefs are then advertised. Applications are assessed for compliance with the commissioning brief, scientific quality, feasibility and value for money.


                                  A commissioner is the person (or organisation) who asks for a piece of research to be carried out.

                                    Commissioning board

                                    A group of experts who consider the scientific merits of grant applications and make recommendations.

                                      Commissioning brief

                                      A detailed description of a question to be answered by new research. In responding to a commissioning brief, researchers outline what studies they would undertake to obtain the information required.


                                        An investigational or marketed product (i.e. active control) or placebo, used as a reference in a clinical trial.

                                          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.


                                            During a research project, the researchers must put data protection measures into place, to ensure that all of the information collected about the participants is kept confidential. This means that the researchers must get the participants’ written permission to look at their medical or social care records. It also means that any information that might identify the participants cannot be used or passed on to others, without first getting the participants’ consent. For example, when researchers publish the results of a project, they are not allowed to include people’s names. This confidentiality will only be broken in extreme circumstances: where it is essential for the person’s care, treatment or safety, where it is required by a court order, for example in a criminal investigation, or where it is necessary to protect the public.


                                              A factor that is 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.


                                                Consultation involves asking members of the public for their views about research, and then using those views to inform decision-making. This consultation can be about any aspect of the research process – from identifying topics for research, through to thinking about the implications of the research findings. Having a better understanding of people’s views should lead to better decisions.


                                                  In health and social care research, the term consumer is used to refer collectively to people who use services, carers, organisations representing consumers’ interests, members of the public who are the potential recipients of services, and groups asking for research to promote good health or because they believe they have been exposed to potentially harmful circumstances, products or services.


                                                    The unintended application of the intervention being evaluated to people in the control group; or unintended failure to apply the intervention to people assigned to the intervention group.

                                                      Contract Research Organisation

                                                      A Contract Research Organisation (CRO) is a company that is contracted by life sciences industry (pharmaceutical, biotechnology, and medical device industries) to support the clinical development process once a new molecule or treatment has been discovered. For example, the CRO may lead and manage the planning, set-up and delivery of clinical trials.


                                                        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.

                                                          Control group

                                                          The comparison group in the randomised trial. Those who are in the control group (or arm) will not receive the new medication, device or treatment that is under study, but will provide a comparison to see how the innovation compares against no treatment or a known treatment.

                                                            Controlled trial

                                                            A type of clinical trial in which observations made during the trial are compared to a standard (called the control). The control may a group of participants in the same trial or observations from outside the trial (for example, from an earlier trial, called a “historical control”).


                                                              An approach in which researchers, practitioners and the public work together, sharing power and responsibility from the start to the end of the project, including the generation of knowledge. The assumption is that those affected by research are best placed to design and deliver it and have skills and knowledge of equal importance.


                                                                The bundle of rights which relates to a work which determines who may publish, copy and distribute it


                                                                  Where two or more organisations share a significant interest in a study, they may elect to act as co-sponsors.

                                                                    Cost effectiveness

                                                                    A measure addressing the cost implications of achieving health benefits. To facilitate comparisons, health benefits can be quantified in terms of ‘QALYs’ (Quality-Adjusted Life Years), which incorporate both extra life achieved and improvements in quality of life. Knowing the cost associated with each QALY gained can help decision-makers assess whether the introduction of a treatment or service should be recommended.

                                                                      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).

                                                                        Creative Commons attribution licence (CC BY)

                                                                        A licence which allows anyone to read, share, and adapt the original material for free, but the user must give appropriate credit and indicate if changes were made.

                                                                          Creative Commons Attribution No-derivatives licence (CC BY-ND)

                                                                          A licence which allows anyone to read and share the original material for free, with appropriate credit (like the CC BY licence), but with the additional restriction that if the reader adapts the original material, they may not distribute the adapted material.

                                                                            Creative Commons Attribution Non-commercial licence (CC BY-NC)

                                                                              Creative Commons public domain dedication (CC0)

                                                                              This is a Creative Commons ‘No rights reserved’ licence, which places materials as completely as possible in the public domain, so that others may freely build upon, enhance and reuse the works for any purposes without restriction under copyright or database law.


                                                                                NIHR’s 23 Clinical Research Facilities (CRFs) are purpose built facilities in NHS hospitals where researchers can deliver early-phase and complex studies.


                                                                                  The CRN makes it possible for patients and health professionals across England to participate in clinical research studies, in both the NHS and in the wider health and social care environment. The CRN provides the infrastructure that allows high-quality clinical research and meets the costs of using NHS staff that support research and provides specialist training so that patients can be confident that research is being delivered by trained, experienced NHS staff. The CRN also meet the costs of using NHS facilities, such as scanners and x-rays that are needed in the course of a study, so that research is not subsidised with funding that has been provided for patient care.

                                                                                    Crossref schema

                                                                                    A metadata standard set by Crossref.