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An individual who is studied in a trial, often, but not necessarily, a patient.


    The act of taking part in a research study, for example people being recruited to take part in a clinical trial or another kind of research study, joining in a focus group or completing a questionnaire.

      Participatory research

      This is a type of research where researchers and people who use services or carers are partners in a research project. The research addresses an issue of importance to service users or carers, who are involved in the design and conduct of the research, and the way the findings are made available. The aim of the research is to improve people’s lives. This isn’t a research method – it’s an approach to research, a philosophy.

        Patient and public involvement

        Also known as PPI, involvement or public involvement. An active partnership between patients and the public and researchers in the research process, rather than the use of people as ‘subjects’ of research. Patient and public involvement in research is often defined as doing research ‘with’ or ‘by’ people who use services rather than ‘to’, ‘about’ or ‘for’ them. This includes, for example, working with research funders to prioritise research, offering advice as members of a project steering group, commenting on and developing research materials, and undertaking interviews with research participants. When using the term ‘public’ we include patients, potential patients, carers and people who use health and social care services as well as people from organisations that represent people who use services.

          Patient information leaflet / patient information sheet

          Researchers must provide a patient information leaflet to everyone they invite to take part in a research study, to ensure people can make an informed decision about this. The leaflet explains what taking part will involve and should include details about: why the research is being done, how long it will last, and what methods will be used; the possible; contact details; how the results will be shared with others.

            Patient Safety Translational Research Centres

            Patient Safety Translational Research Centres (PSTRCs) conduct and support research to investigate ways to improve the safety, quality and effectiveness of the services that the NHS provides to its patients.


              A method of restricting access to content, (e.g., research articles, news), via a purchase or a paid-for subscription.


                NIHR Programme Development Grants (PDG) support researchers to carry out targeted preparatory work to strengthen an application for future full Programme Grants for Applied Research (PGfAR) funding award.

                  Peer interviewing

                  Peer interviewing is where people are interviewed by others who have a similar experience to them – their peers. For example, in a project to find out about children’s experiences of after school care, children with experience of using after school care may act as peer interviewers, asking other children about their experience. Some researchers believe that this kind of interviewing enables people to talk more freely about their experience.

                    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.

                      Persistent Identifier

                      (PID) A long-lasting reference to a resource.

                        Perspectives / user perspectives

                        A user perspective is often what people with experience of using health or social services are asked to bring when they get involved in research. They are asked to provide ideas, comments and suggestions based on the unique insight they have from their knowledge and experience of life with a health condition. They cannot be representative of everyone who uses a particular service, but they can offer their own perspective, and often that of other people.


                          NIHR Programme Grants for Applied Research (PGfAR) funds collaborative, multidisciplinary programmes of applied research to solve health and social care challenges.


                            Public Health Intervention Responsive Studies Teams


                              The PHR Programme evaluates interventions taking place outside of the NHS that aim to improve public health.

                                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.


                                  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.


                                    An online archive of scholarly materials.


                                      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.


                                        Patient and Public Involvement. In research, PPI takes various forms, from involvement of public contributors in priority setting, representation on committees, and as reviewers. NIHR appoint public board and panel members via open competition.

                                          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.

                                            Preclinical study

                                            Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.


                                              A complete scientific manuscript (often one also being submitted to a peer-reviewed journal) that is uploaded by the authors to a preprint repository or service, typically without formal peer review of that version, such as would be undertaken by a publisher for a scholarly journal.

                                                Primary outcome

                                                The outcome of greatest importance.

                                                  Primary research

                                                  Experimental studies generating new data (cf. secondary research, which analyses existing data).

                                                    Principal investigator

                                                    The principal investigator (PI) may be the chief investigator, or where the research is taking place across than one site, the principal investigator is the person at each site who is responsible for the day to day running of the research project.


                                                      Rigorously examining potential topics for research to identify their importance and where the need for new evidence is greatest.


                                                        The chance or risk of something happening.


                                                          The plan or set of steps to be followed in a study.


                                                            The NIHR Policy Research Programme (PRP) enables evidence informed policy making in health and social care.


                                                              NIHR Policy Research Units (PRUs) undertake research to inform government and arms-length bodies making policy decisions about health and social care. The units create a critical mass of experts for research in priority areas for health and social care policy.


                                                                Patient Safety Translational Research Centres (PSTRCs) conduct and support research to investigate ways to improve the safety, quality and effectiveness of the services that the NHS provides to its patients.

                                                                  Public contributor

                                                                  Public contributor is an umbrella term used to describe members of the public who take part in patient and public involvement activities. We use the definition of 'public' to include patients, potential patients, carers and people who use health and social care services as well as people from organisations that represent people who use services.

                                                                    Public health research

                                                                    Public health is concerned with promoting good health, preventing disease and protecting people from hazards, rather than treating illnesses. It covers topics like the control of infectious diseases, vaccinations, and helping people to adopt healthy lifestyles. Public health research involves finding out new knowledge (or testing out existing ideas) to do with public health – so it might address questions about the best ways to help people stop smoking or how flu spreads.

                                                                      Public Partnerships

                                                                      A term to collectively describe ways in which patients, service users, carers and members of the public work with researchers, and health and care professionals, in the creation and use of health and care research. Public partnerships encompasses participation, involvement and engagement; they are all important in the process of creating and making use of high quality research. Each can take place in isolation, or in parallel. Experience, as well as research, has shown that they are mutually supportive in making research as relevant and impactful as possible. Use of the term Public Partnerships is not intended to replace, or make redundant, any existing terms or preferred ways of describing things.

                                                                        Publishing platform

                                                                        The publishing platform for the original publication of research articles. Platforms that merely serve to aggregate or re-publish content that has already been published elsewhere are not considered as such.

                                                                          PubMed Central

                                                                          A permanent, free-to-access online digital repository operated by the United States National Library of Medicine, which contains full-text preprints and peer-reviewed life sciences publications.