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.


National collaborating centre (NCC)

A group set up by NICE to develop NICE clinical guidelines for a particular disease area. Each centre is based at one of the Royal Medical Colleges. Staff at the national collaborating centre appraise the evidence for a guideline and put together a guideline development group. There are four national collaborating centres:

  • National Clinical Guideline Centre for Acute and Chronic Conditions
  • National Collaborating Centre for Cancer
  • National Collaborating Centre for Mental Health
  • National Collaborating Centre for Women's and Children's Health
National service frameworks

National service frameworks (NSFs) are published by the Department of Health. They establish a set of minimum national standards for clinical care and treatment and to prevent ill health and encourage good health. The aim is to improve standards and reduce local variations in service. See

Net benefit

The financial benefit from a test, treatment or procedure, minus its total cost.

For example, if a patient's illness costs 1000 each year (for example because of reduced earnings) and a treatment reduces this to 800 a year (a saving of 200), then if the treatment costs 50, the net benefit would be 200 − 50, that is 150.

NHS trusts

A trust is an NHS organisation responsible for providing certain healthcare services. An acute trust provides hospital services. A mental health trust provides most mental health services. A primary care trust provides local, non-hospital based services and also commissions hospital care on behalf of the local population.

NICE clinical guideline

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

NICE evidence review

A NICE evidence review summarises the main points and trends highlighted in the research literature on a specific topic. A review is considered non-systematic unless all aspects of the topic are covered and an objective appraisal has been carried out to determine the quality of the studies involved.

NICE interventional procedures guidance

NICE guidance about whether an interventional procedure is safe enough and works well enough to be used in the NHS. The term 'interventional procedure' means any surgery, test or treatment that involves entering the body through skin, muscle, a vein or artery, or a body cavity.

NICE public health guidance

Guidance on ways to help people reduce their risk of illness and lead a healthier life. NICE public health guidance may look at a particular type of activity (intervention) that helps to reduce people's risk of developing a disease or condition or help to promote or maintain a healthy lifestyle, or deal with broad action for the promotion of good health and the prevention of ill-health.

Advice on interventions covers single topics, such as giving advice in GP practices to encourage exercise, providing a needle exchange scheme for injecting drug users or providing breastfeeding support for new mothers. Advice on broader actions could focus on a topic such as smoking, or issues such as improving the general physical environment to encourage people to exercise more. (This could involve, for example, regulations on building design, road building, city centres and access to public buildings and spaces.)

NICE technology appraisal guidance

NICE technology appraisal guidance makes recommendations on the use of new and existing drugs and treatments in the NHS. If NICE recommends a drug or treatment for a particular condition, the NHS has to make it available for patients with that condition if it is suitable for them. Usually, this has to be done within 3 months of the guidance being issued.

Some technology appraisal guidance covers surgical procedures. If a procedure is recommended it should be made available in the NHS. This is different from NICE interventional procedures guidance, which is about whether a procedure is safe and effective enough to be used routinely in the NHS. A recommendation in interventional procedures guidance that a procedure is safe to use does not mean that the NHS has to offer the procedure.


See Number Needed to Treat.

Nominal group technique

A technique used to reach agreement on a particular issue. See also consensus methods.

Non-experimental study

Participants are selected on the basis of their availability, with no attempt to avoid bias. See experimental study and quasi-experimental study.

Non-randomised controlled trial

A clinical trial with a control group in which patients are not put in the study or control group by chance (randomisation). Instead, they are sorted using other methods.

Non-systematic review

See NICE evidence review.

Number needed to harm (NNH)

The average number of patients who could be treated before an adverse event would occur. For example, if the NNH is four, then - on average - for every 4 patients treated, one bad outcome would occur. It is the opposite of absolute risk reduction. The closer the NNH is to one, the more likely it is that someone on the treatment will experience an adverse event.

For example, if you give a stroke prevention drug to 100 people and two of them experience joint pain, the number needed to harm is 50 (that is, 100 divided by two equals 50).

Number needed to treat (NNT)

The average number of patients who need to be treated to get a positive outcome. For example, if the NNT is four, then 4 patients would have to be treated to ensure one of them gets better. The closer the NNT is to one, the better the treatment.

For example, if you give a stroke prevention drug to 20 people before one stroke is prevented, the number needed to treat is 20. See also number needed to harm, absolute risk reduction.

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This page was last updated: 15 April 2011

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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.