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.

  • Cancer service guidance

    Guidance on the way services are organised for the treatment of different types of cancer. NICE no longer produces cancer service guidance, but existing guidance is still available.
  • Care pathway

    The route a person takes through healthcare services. For example, a care pathway might show the order in which various tests are done to diagnose an illness, which treatments should be tried, and when care moves from primary to secondary care, or from hospital back into community care.
  • Carer

    Someone who looks after family, partners or friends in need of help because they are ill, frail or have a disability.
  • Case-control studies

    A study to find out the cause(s) of a disease or condition. This is done by comparing a group of patients who have the disease or condition (cases) with a group of people who do not have it (controls) but who are otherwise as similar as possible (in characteristics thought to be unrelated to the causes of the disease or condition). This means the researcher can look for aspects of their lives that differ to see if they may cause the condition.
    For example, a group of people with lung cancer might be compared with a group of people the same age that do not have lung cancer. The researcher could compare how long both groups had been exposed to tobacco smoke. Such studies are retrospective because they look back in time from the outcome to the possible causes of a disease or condition.
  • Centre for Clinical Practice

    The centre at NICE that is responsible for guidelines on clinical topics. These are recommendations, based on the best available evidence, on the appropriate diagnosis, treatment and care of people with specific diseases and conditions. Guidelines are developed by independent Guideline Development Groups, supported by a National Collaborating Centre, or by a team at NICE.
  • Centre for Health Technology Evaluation

    The centre at NICE that is responsible for producing technology appraisals, and interventional procedure, medical technology and diagnostics guidance. The guidance is developed by independent committees.
    Technology appraisal guidance makes recommendations on the use of new and existing technologies in the NHS. Interventional procedure guidance evaluates the safety and efficacy of procedures used for diagnosis or treatment. The Medical Technologies Programme evaluates innovative medical technologies.The Diagnostics Assessment Programme evaluates diagnostic technologies.
  • Centre for Public Health

    The centre at NICE that is responsible for producing guidelines on public health topics. These are recommendations, based on the best available evidence, about preventing ill health and promoting good health. The guidelines are developed by independent Public Health Advisory Committees.
  • Citizens Council

    An advisory body made up of 30 members of the public, representing the UK. The Council considers any social and moral issues raised by NICE's recommendations and produces reports for NICE that reflect the public's perspective on the issue. These are used to help write NICE's 'Social value judgements' document. This sets out the principles that guidance developers should follow when deciding which treatments to recommend.
  • Clinical audit

    A process for monitoring standards of clinical care to see if it is being carried out in the best way possible (known as 'best practice').
    Clinical audit can be described as a systematic 'cycle'. It involves measuring care against specific criteria, taking action to improve it if necessary, and monitoring the process to sustain improvement. As the process continues, an even higher level of quality is achieved.
  • Clinical impact

    The effect that something is likely to have on the treatment of a particular group of people - or on the results of treating that group.
  • Clinical importance or significance

    A benefit from treatment that relates to an important outcome such as length of life, and is large enough to be important to patients and health professionals. As an example, it might include a general reduction in symptoms, less pain or lower blood pressure.
    Effects identified as statistically significant are not always clinically significant, because the effect is small or the outcome is not important. For example, if a treatment improves blood flow but there is no evidence that this leads to an important clinical outcome, such as lower risk of blood clots or heart attack.
  • Clinical trial

    A study to determine whether a treatment is safe and effective. It is carried out with a sample of patients, usually after laboratory studies and studies with healthy volunteers have been conducted. The trial is set up to answer 1 or more questions. For example, does the treatment have any adverse side effects? If so, how serious are they?
  • Clinician

    A healthcare professional who provides patient care. For example, a doctor, nurse or physiotherapist.
  • Cochrane Collaboration

    An international organisation that produces systematic review of the evidence from randomised controlled trials relating to a particular health problem or healthcare intervention. See also Cochrane Library.
  • Cochrane Library

    A regularly updated collection of evidence-based health databases including the Cochrane Database of Systematic Reviews, which contains reviews on a variety of health topics.
  • Code of conduct for NICE committees

    A code of conduct developed by NICE for members of guidance committees, and other people who attend committee meetings. This code sets out the responsibilities of NICE and the committee, and the principles of transparency and confidentiality.
  • Cohort study

    A study with 2 or more groups of people - cohorts - with similar characteristics. One group receives 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.
  • Commentator

    Commentators are invited by NICE to take part in the appraisal process and comment on the various documents produced during the process. Unlike consultees, commentators cannot appeal against the final appraisal determination.
  • Commissioning

    The process used by health services and local authorities to: identify the need for local services; assess this need against the services and resources available from public, private and voluntary organisations; decide priorities; and set up contracts and service agreements to buy services. As part of the commissioning process, services are regularly evaluated.
  • Comparability

    Similarity of groups in terms of characteristics likely to affect study results (such as health status or age).
  • Comparator

    The standard intervention against which an intervention is compared in a study. The comparator can be no intervention (for example, best supportive care).
  • Confidence interval

    The confidence interval (CI) is a way of expressing how certain we are about the findings from a study, using statistics. It gives a range of results that is likely to include the 'true' value for the population.
    The CI is usually stated as '95% CI', which means that the range of values has a 95 in a 100 chance of including the 'true' value. For example, a study may state that 'based on our sample findings, we are 95% certain that the 'true' population blood pressure is not higher than 150 and not lower than 110'. In such a case the 95% CI would be 110 to 150.
    A wide confidence interval indicates a lack of certainty about the true effect of the test or treatment - often because a small group of patients has been studied. A narrow confidence interval indicates a more precise estimate (for example, if a large number of patients have been studied).

  • Conflict of interest

    An interest that might conflict, or be perceived to conflict, with a person's duties and responsibilities during guidance development. NICE staff, contractors and Committee members declare any potential interests, and do not take part in discussions in which they have a conflict of interests (for example, because they are doing consultancy work for another organisation).
  • Confounding

    In a study, confounding occurs when the effect of an intervention on an outcome is distorted as a result of an association between the population or intervention or outcome and another factor (the 'confounding variable' or 'confounder') that can influence the outcome independently of the intervention under investigation.
    For example, a study of heart disease may look at a group of people that exercises regularly and a group that does not exercise. If the ages of the people in the 2 groups are different, then any difference in heart disease rates between the 2 groups could be because of age rather than exercise. Therefore age is a confounding factor.
  • Consensus methods

    Techniques that aim to reach an agreement on a particular issue. Formal consensus methods include Delphi and nominal group techniques, and consensus development conferences. When developing NICE guidelines, consensus methods may be used where there is a lack of strong research evidence on a particular topic
  • Consensus statement

    A statement based on the collective views of a body of experts.
  • Consistency

    The degree of similarity between the conclusions of different studies on the same topic. See also homogeneity.
  • Consultation

    The period during guidance development when stakeholders or interested members of the public can comment on draft guidance. For guidelines and technology appraisals, there is also a consultation on the draft scope.
  • Consultee

    An organisation or individual invited to comment during development of technology appraisal or interventional procedures guidance. Consultees can submit evidence, comment on the draft documents and appeal against the Appraisal Committee's final recommendations.
  • Control group

    A group of people in a study who do not receive the treatment or test being studied. Instead, they may receive the standard treatment (sometimes called 'usual care') or a dummy treatment (placebo). The results for the control group are compared with those for a group receiving the treatment being tested. The aim is to check for any differences.
    Ideally, the people in the control group should be as similar as possible to those in the treatment group, to make it as easy as possible to detect any effects due to the treatment.
  • Controlled clinical trial

    A study testing a specific treatment by using 2 (or more) groups of patients. The experimental group receives the treatment being tested. The comparison (or control) group receives an alternative treatment, a dummy treatment (placebo) or no treatment. The 2 groups are compared to see how effective the experimental treatment was.
    If participants are randomly allocated to treatment and comparison groups, this is called a randomised controlled trial.
  • Cost-benefit analysis

    One of the tools used to carry out an economic evaluation. The costs and benefits are measured using the same monetary units (for example, pounds sterling) to see whether the benefits exceed the costs.
  • Cost-consequence analysis

    One of the tools used to carry out an economic evaluation. This compares the costs (such as treatment and hospital care) and the consequences (such as health outcomes) of a test or treatment with a suitable alternative. Unlike cost-benefit analysis or cost-effectiveness analysis, it does not attempt to summarise outcomes in a single measure (such as the quality-adjusted life year) or in financial terms. Instead, outcomes are shown in their natural units (some of which may be monetary) and it is left to decision-makers to determine whether, overall, the treatment is worth carrying out.
  • Cost-effectiveness analysis

    Cost-effectiveness analysis assesses the cost of achieving a benefit by different means. The benefits are expressed in non-monetary terms related to health, such as symptom-free days, heart attacks avoided, deaths avoided or life years gained (that is, the number of years by which life is extended as a result of the intervention).
  • Cost-minimisation analysis

    One of the tools used to carry out an economic evaluation. Cost-minimisation analysis compares the costs of different interventions that provide the same benefits. If they are equally effective, only the costs are compared and the cheapest intervention will provide the best value for money. In practice, there are relatively few cost-minimisation analyses because it is rare for 2 healthcare interventions to provide exactly the same benefits.
  • Cost-utility analysis

    One of the tools used to carry out an economic evaluation. The benefits are assessed in terms of both quality and duration of life, and expressed as quality-adjusted life years (QALYs). See also utility.
  • Critical appraisal

    Reviewing a piece of research or a systematic review of the evidence to judge the quality of the method used and the content. Critical appraisals are also used to judge the effectiveness of a test or treatment that is being studied.
  • Cross-over study design

    A study comparing 2 or more treatments. Once participants have completed a course of 1 treatment they are switched to a different treatment. For example, for a comparison of treatments A and B, half of participants would receive A first followed by B. The other half would receive treatment B first.
  • Cross-sectional study

    A 'snapshot' observation of a set of people at 1 time. This type of study contrasts with a longitudinal study, which follows a set of people over a period of time.
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