The NICE Glossary provides brief definitions and explanations of terms used on our site. The terms describe how we work and how our guidance is produced.

Our glossary excludes specific clinical and medical terms. If you cannot find the term you are looking for, please email us so that we can consider adding it to the glossary.

Some definitions and examples are based on those in the 'HTAi consumer and patient glossary', with thanks to Health Technology Assessment International.

  • P value

    The p value is a statistical measure that indicates whether or not an effect is statistically significant.
    For example, if a study comparing 2 treatments found that 1 seems more effective than the other, the p value is the probability of obtaining these results by chance. By convention, if the p value is below 0.05 (that is, there is less than a 5% probability that the results occurred by chance) it is considered that there probably is a real difference between treatments. If the p value is 0.001 or less (less than a 1% probability that the results occurred by chance), the result is seen as highly significant.
    If the p value shows that there is likely to be a difference between treatments, the confidence interval describes how big the difference in effect might be.
  • Patient access scheme

    A way for pharmaceutical companies to make high-cost drugs affordable for the NHS. Manufacturers and/or sponsors may submit a patient access scheme proposal for any technology going through the NICE single or multiple technology appraisal processes. For example, the company might pay for the drugs for an introductory period for each patient, and then the NHS would take over the payments if the drug is shown to work for that person; or the NHS might pay for the first course of a drug and the company would take over the payments if the patient needs treatment for longer than average.
    Each proposal is assessed by the Patient Access Scheme Liaison Unit.
  • Patient Access Scheme Liaison Unit

    A team at NICE that coordinates the review and evaluation of patient access scheme proposals and advises the Department of Health on whether they should be accepted.
  • Patient and carer organisations

    Organisations of patients, carers, communities and other lay members, including those that represent people from groups protected by equalities legislation.
  • Peer review

    Review of a study, service or recommendation by those with similar interests and expertise to the people who produced it to make sure the study results are accurate and valid. Peer reviewers can include both professionals and 'lay' experts. Lay experts are people whose expertise derives from their personal experience rather than formal training.
  • PICO (population, intervention, comparison and outcome) framework

    A structured approach for developing review questions that divides each question into 4 components: the population (the population under study); the interventions (what is being done); the comparators (other main treatment options); and the outcomes (measures of how effective the interventions have been).
  • Pilot study

    A small-scale 'test' of a particular approach. For example, a new questionnaire could be piloted with a small group of people before it is sent out to a wider audience. The aim would be to highlight any problems or areas of concern and amend it before the full-scale study begins.
  • Placebo

    A fake (or dummy) treatment given to participants in the control group of a clinical trial. It is indistinguishable from the actual treatment (which is given to participants in the experimental group). The aim is to determine what effect the experimental treatment has had - over and above any placebo effect caused because someone has received (or thinks they have received) care or attention.
  • Population

    A group of people with a common link, such as the same medical condition or living in the same area or sharing the same characteristics. The population for a clinical trial is all the people the test or treatment is designed to help (such as adults with diabetes). The group taking part in a clinical trial need to be typical of the whole population of interest.
  • Positive predictive value

    The proportion of people with a positive test result who actually have the disease or characteristic.
  • Premeeting briefing

    A document that summarises the findings from the evidence for a single technology appraisal. It is used to support the Appraisal Committee in their decision making about the drug, treatment or procedure.
  • Primary care

    Healthcare delivered outside hospitals. It includes a range of services provided by GPs, nurses, health visitors, midwives and other healthcare professionals and allied health professionals such as dentists, pharmacists and opticians. It includes community clinics, health centres and walk-in centres.
  • Process

    NICE processes are the actions involved in producing NICE guidance or other advice or resources (such as implementation tools). When producing NICE guidance, the process includes: deciding what it will cover (the scope), setting up a group of experts who will look at the evidence and make recommendations, and a consultation with professionals and the public on draft guidance.
  • Prognosis

    A probable course or outcome of a disease. Prognostic factors are patient or disease characteristics that influence the course. Good prognosis is associated with low rate of undesirable outcomes; poor prognosis is associated with a high rate of undesirable outcomes.
  • Proprietary name

    The brand name given by the manufacturer to a drug or device it produces.
  • Prospective cohort study

    An observational study that takes a group (cohort) of patients and follows their progress over time in order to measure outcomes such as disease or mortality rates and make comparisons according to the treatments or interventions that patients received. Prospective cohorts are assembled in the present and followed into the future.
  • Prospective study

    A research study in which the health or other characteristic of participants is monitored (or 'followed up') for a period of time, with events recorded as they happen. This contrasts with retrospective studies.
  • Protocol

    A plan or set of steps that defines how something will be done. Before carrying out a research study, for example, the research protocol sets out what question is to be answered and how information will be collected and analysed.
  • Public health

    Public health is about helping people to stay healthy and avoid getting ill, so this includes work on a whole range of policy areas such as immunisation, nutrition, tobacco and alcohol, drugs recovery, sexual health, pregnancy and children's health.
  • Public Health England

    An executive agency that delivers services to protect the public's health through a nationwide integrated health protection service, provides information and intelligence to support local public health services, and supports the public in making healthier choices.
  • Public Involvement Programme

    A department in NICE that advises on involving patients, carers and the public in NICE's work. It also supports patients, carers and members of the public who are involved in producing NICE guidance, and stakeholder organisations that contribute to NICE's work.
  • Publication bias

    Publication bias occurs when researchers publish the results of studies showing that a treatment works well and don't publish those showing it did not have any effect. If this happens, analysis of the published results will not give an accurate idea of how well the treatment works. This type of bias can be assessed by a funnel plot.
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