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

Our glossary excludes specific clinical and medical terms although we intend to include these in the longer term. If you cannot find the term you are looking for, please email us so that we can consider adding it to the glossary. New terms are added regularly.

The glossary is not used for indexing the site or for navigation - for information on this, please see the NICE taxonomy.

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. We no longer produce cancer service guidance, but existing guidance is still in force.


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

Case report or case study

A detailed report on one patient (or case), that describes their treatment and the outcome (in terms of their health condition or disease status).

Case series study

Description of several cases of a given disease, usually covering the course of the disease and the response to treatment in each case. There is no comparison (control) group.

Case-control study

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.

Causal relationship

This describes the relationship between two variables if it can be established that one has a direct effect on the other. Usually randomised controlled trials are needed to find out whether there is a causal relationship.

Proving cause and effect is not just about showing a link between two variables. For example, if everyone who had eaten a particular food became sick and everyone who avoided it remained well, then the food would be clearly associated with the sickness. But even if leftovers were found to be contaminated, it could not be proved that the food caused the sickness unless all other possible causes (for example, environmental factors) had been ruled out.


See Controlled clinical trial.

Centre (see also Directorate)

Centres are the departments in NICE that produce specific types of guidance:

Directorates are departments that provide services across the whole of NICE.

Centre for Clinical Practice

The department at NICE that manages the development of clinical guidelines. It commissions one of the national collaborating centres to develop each clinical guideline.

Centre for Health Technology Evaluation

The department in NICE that is responsible for producing technology appraisals and interventional procedures guidance. The guidance is developed by independent committees - the Appraisal Committee and the Interventional Procedures Advisory Committee.

Centre for Public Health Excellence

The department in NICE that is responsible for producing public health guidance.


Control Event Rate - see Event rate.


See study checklist.

Citizens Council

A group of 30 people who bring the views of the public to NICE's decision-making. The Council considers questions about values - including fairness and need - and its reports are used to help write NICE's 'social value judgements' document. This sets out principles that the groups who write NICE guidance follow when deciding what treatments to recommend. Citizens Council members are appointed for 3 years.

Citizen's Council Committee

Decides the questions to be put to the Citizens Council, in consultation with the rest of NICE. It is a sub-committee of the Board.

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' or 'spiral'. 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, each 'cycle' moves to a higher level of the 'spiral', that is, an even higher level of quality is achieved.

Clinical effectiveness

How well a specific test or treatment works when used in the 'real world' (for example, when used by a doctor with a patient at home), rather than in a carefully controlled clinical trial. Trials that assess clinical effectiveness are sometimes called management trials.

Clinical effectiveness is not the same as efficacy.

Clinical governance

All NHS organisations have a statutory duty to continually monitor and improve clinical care. This process, known as 'clinical governance', ensures high standards of care, safeguards patients against poor performance and reduces variation in services.

Clinical guideline (CG)

NICE guidance on the treatment and care of people with a specific disease or condition in the NHS.

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 pathway

This usually refers to the sequence of practices, procedures and treatments that should be used with people with a particular condition. The aim is to improve the quality of care. It is sometimes also known as a 'care pathway'.

Clinical question

A question used to search for evidence as part of the development of NICE clinical guidelines. When a clinical question is precisely formulated to look for evidence on a very particular part of a topic, it is called a focused question. See also Research question.

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 one or more questions. For example, does the treatment have any adverse side effects? If so, how serious are they? See also controlled clinical trials and randomised controlled trials.


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


A group of patients (rather than one person) that is assessed as a single 'unit' in a study. See also cluster design, cluster randomisation.

Cluster design study

A study that involves a group of subjects, with the results reported for the group rather than for individuals. For example, if all patients in a general practice are given the same treatment, the general practice is a cluster. See also cluster, cluster randomisation study.

Cluster randomisation study

Clusters or groups of patients are randomly allocated for tests or treatment. For example, in a study examining two hospital treatments, hospital wards may be the clusters. Each ward within the study would be randomly allocated to administer one of the two tests or treatments. See also cluster, cluster design study.

Cochrane Collaboration

An international organisation that finds, appraises and reviews randomised controlled trials. 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. The Cochrane Library is available on CD-ROM and the Internet. See also Cochrane Collaboration.


A group used as part of a research study. The group is made up of people sharing a common characteristic (for example, pupils in the same school year).

Cohort study

A study with two 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. See also observational study.

Combined modality

Use of two or more treatments together (for example, surgery, chemotherapy and radiotherapy may be used together to treat cancer).

Commentator (see also Consultee and Stakeholder)

An organisation invited to comment on a technology appraisal. Commentators can comment on the evidence and other documents but are not asked to submit evidence. Commentators include:

  • manufacturers of drugs or treatments that the drug or treatment being appraised is being compared with
  • NHS Quality Improvement Scotland
  • research groups working on the same or similar topics.
Commercial 'in confidence' material

Information (for example, the findings of a research project) defined as 'confidential' because its public disclosure could have an impact on the commercial interests of a particular company. (Academic 'in confidence' material is information - usually work produced by a research or professional organisation - that is awaiting publication.)


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.

Commissioning guides

Tools available on NICE's website to help senior healthcare professionals and health service managers with decisions when they are commissioning services in clinical areas for which NICE has issued guidance.


A disease or condition that someone has in addition to the health problem being studied or treated.

Confidence interval (CI)

There is always some uncertainty in research. This is because a small group of patients is studied to predict the effects of a treatment on the wider population. The confidence interval 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).

Confounder or confounding factor

Something that influences a study and can result in misleading findings if it is not understood or appropriately dealt with.

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 two groups are different, then any difference in heart disease rates between the two groups could be because of age rather than exercise. Therefore age is a confounding factor.

Consensus methods

Techniques used to reach agreement on a particular issue. Consensus methods may be used to develop NICE guidance if there is not enough good quality research evidence to give a clear answer to a question. Formal consensus methods include Delphi and nominal group techniques.

Consensus statement

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


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


A stage during the development of all NICE guidance, when organisations can comment on draft guidance. These organisations must be registered with NICE as commentatorsand consultees(for technology appraisals), consultees(for interventional procedures) or stakeholders(for clinical guidelines and public health guidance).

For clinical guidelines, public health guidance and technology appraisals, there is also a consultation on the draft scope.

Consultee (see also Commentator and Stakeholder)

An organisation invited to take part in a technology appraisal. Consultees can submit evidence during the appraisal, comment on the appraisal documents and appeal against the Appraisal Committee's final recommendations (the final appraisal determination). Consultee organisations include:

  • national groups representing patients and carers
  • bodies representing healthcare professionals
  • manufacturers of the treatment being appraised.

A factor (such as high blood pressure or use of another medicine at the same time) that increases the risk of a side effect from a particular treatment. Usually the treatment will not be recommended for people with such a contraindication.


A standard or measure for avoiding bias from confounders in an experiment. In clinical trials, the control may be a suitable known treatment, test, risk factor etc. In a case-control study, the controls are usually the people who do not have the condition (control group).

Control event rate

See event rate.

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 (CCT)

A study testing a specific treatment by using two (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 two 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 effectiveness

Value for money. A test or treatment is said to be 'cost-effective' if it leads to better health than would otherwise be achieved by using the resources in other ways.

Cost-benefit analysis

Cost-benefit analysis is 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

Cost-consequence analysis is 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 (like 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 is one of the tools used to carry out an economic evaluation. 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).

Costing report and costing template

Documents that help with analysing the overall costs of putting the guidance into practice and any savings. These are published with most pieces of NICE guidance (except interventional procedures guidance).
The costing report summarises the national costs. The costing template helps local NHS organisations to work out how much it will cost to implement the guidance in their area, and how much they could save.
For technology appraisal guidance a combined costing report/template is produced, whereas there are separate documents for clinical guidelines and public health guidance.
If a piece of guidance is not expected to have a significant impact on costs, a costing statement is produced instead.

Costing statement

A short statement that is published if there are not likely to be significant costs involved in implementing a piece of NICE guidance.

Cost-minimisation analysis

Cost-minimisation analysis is 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 two healthcare interventions to provide exactly the same benefits.

Cost-per-QALY analysis

Another name for a cost-effectiveness analysis. The benefits of different treatments or tests are stated as quality-adjusted life years (QALYs).

Cost-utility analysis

Cost-utility analysis is 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 two or more treatments. Once participants have completed a course of one 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 one time. This type of study contrasts with a longitudinal study, which follows a set of people over a period of time.

Back to top

This page was last updated: 15 April 2011

Accessibility | Cymraeg | Freedom of information | Vision Impaired | Contact Us | Glossary | Data protection | Copyright | Disclaimer | Terms and conditions

Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.

Selected, reliable information for health and social care in one place

Accessibility | Cymraeg | Freedom of information | Vision Impaired | Contact Us | Glossary | Data protection | Copyright | Disclaimer | Terms and conditions

Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.