The NICE glossary provides brief definitions and explanations of terms used on the website. The terms describe how NICE works and how its 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.

For terms used in social care, the Care and Support Jargon Buster from Think Local Act Personal is a useful guide to the most commonly used social care words and phrases, and what they mean.

  • 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 to be 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 0.1% probability that the results occurred by chance), the result is seen as highly significant. 

    However, a statistically significant difference is not necessarily clinically significant. For example, drug A might relieve pain and stiffness statistically significantly more than drug B. But, if the difference in average time taken is only a few minutes, it may not be clinically significant. See Minimal clinically important difference.

    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.

  • Parameter

    A measurable or quantifiable characteristic. For example, the relative treatment effect of a technology may be a parameter in an economic model.

  • Parameter uncertainty

    Uncertainty about the mean values of parameters (for example, health outcomes, utilities and resource use) included in the model.

  • Patient access scheme

    A way for pharmaceutical companies to make high-cost drugs affordable for the NHS. Companies may submit a patient access scheme proposal for any technology going through the NICE single or multiple technology appraisal processes, and highly specialised medicines process. 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 decision aid

    A tool that presents evidence-based estimates of the benefits and risks of the available treatment options in sufficient detail that people are better able to judge their value. In contrast to health education materials, patient decision aids (PDAs) are tailored to a person’s health status and help them to make specific, personal choices about their treatment. The values and perceptions of individual people, and their attitudes to risk, may be different from those of their clinician. Importantly, PDAs are intended to supplement or support the interaction between the person and their clinician, rather than replace it.

  • 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.
  • Per-protocol analysis

    A comparison of treatment groups in a trial that includes only those patients who completed the treatment they were originally allocated to. If done alone, this analysis leads to bias.

  • Personal social services

    Care services for vulnerable people, including those with special needs because of old age or physical disability and children in need of care and protection. Examples are residential care homes for older people, home help and home care services, and social workers who provide help and support for a wide range of people (Department of Health definition).

  • PICO

    A PICO (population, intervention, comparison and outcome) framework is a structured approach for developing review questions. It divides each question into 4 components: the population (the population being studied); 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 patients in the control group of a clinical trial. It is indistinguishable from the actual treatment (which is given to patients 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 had (or thinks they have had) 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 of people 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. It is different from sensitivity.

  • Premeeting briefing

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

  • Prevalence

    How common a disease or condition is within a population, either at a point in time or over a given period of time (it includes new and existing cases). It is different from incidence.

  • 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.
  • Primary data

    Data collected and used for a specific research purpose.

  • Prioritisation board

    A unified and integrated NICE committee that makes decisions on topic selection and prioritisation for guidance development across all NICE work programmes, and which maintains oversight of NICE’s guidance portfolio.

  • Probabilistic sensitivity analysis

    Probability distributions are assigned to the uncertain parameters and are incorporated into evaluation models based on decision analytical techniques (for example, Monte Carlo simulation).

  • Process

    NICE processes are the actions involved in producing NICE guidance or other advice or resources (such as tools to support implementation ). 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

    Prognosis describes the likelihood of a particular outcome in the future, such as disease progression, the development of higher levels of need, or length of survival after diagnosis or for a person with a particular set of risk markers. A prognosis is based on the characteristics of the person (‘prognostic factors’). These prognostic factors may be disease specific (such as the presence or absence of a particular disease feature), demographic (such as age or sex), or related to other aspects of the person’s health status (such as the presence of comorbidities). A prognostic factor does not need to be the cause of the outcome, but should be associated with (in other words, predictive of) that outcome. Good prognosis is associated with a low rate of undesirable outcomes; poor prognosis is associated with a high rate of undesirable outcomes.

  • Propensity score

    The estimated probability of being assigned to a particular intervention conditional on a set of observed covariates.

  • Proprietary name

    The brand name given by the company for a drug or device it produces.

  • Prospective cohort study

    An observational study with 2 or more groups (cohorts) of people with similar characteristics. One group has a treatment, is exposed to a risk factor or has a particular symptom and the other group does not. The study follows their progress over time and records what happens.

  • Prospective study

    A research study in which the health or other characteristic of patients 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 Involvement Programme

    Advises NICE on involving patients, carers and the public in its 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 do not publish those results 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.