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.

  • Absolute risk

    The likelihood of an event or outcome occurring (for example, an adverse reaction to the drug being tested) among the group being studied. Studies that compare 2 or more groups of people may report results in terms of the absolute risk reduction.

  • Absolute risk reduction

    A reduction in the likelihood of an event or outcome occurring as a result of a treatment or another intervention. For example, if a treatment reduces the absolute risk of death from 0.25 (25%) to 0.10 (10%), the absolute risk reduction (ARR) is 0.15 (15%), that is, 0.25 minus 0.10.

    The estimate of absolute risk reduction often comes from clinical trials. The percentage of people taking part who are receiving treatment (treatment group) and experience a specific outcome is compared with the percentage of people taking part but not receiving treatment (control group) who experience the same outcome.

  • Acute sector

    Hospital-based healthcare services for inpatients, outpatients and people having day-case treatments.
  • AGREE (appraisal of guidelines research and evaluation)

    An international collaboration of researchers and policy makers whose aim is to improve the quality and effectiveness of practice guidelines. The AGREE II instrument, developed by the group, is designed to assess the quality of clinical guidelines.
  • Allocation concealment

    The process used to prevent advance knowledge of group assignment in a randomised controlled trial. The allocation process should be uninfluenced by the person making the allocation, by being administered by someone who is not responsible for recruiting participants.
  • Analysis

    The process of looking for patterns in information to identify cause and effect or answer specific questions, such as whether a treatment works and what the risks are.
    There are 2 types of analysis. Quantitative analysis looks for patterns in the form of numbers, such as most frequent choice of treatment option or average rating of pain during treatment. Qualitative analysis looks for patterns of meaning, feeling or beliefs. It can lead to a finding such as 'most people who support paying more for end of life therapy also believe society should give more to those with greater need.'
  • Appeals process

    The final part of the process for producing technology appraisal guidance. Organisations representing patients and carers, healthcare professionals and manufacturers can appeal against final advice given by the independent appraisal committee on a specific medicine or treatment. The grounds for appeal are that NICE has failed to act fairly, or has exceeded its powers; or that a recommendation is unreasonable in light of the evidence submitted.
  • Applicability

    The degree to which the results of an observation, study or review are likely to hold true in a particular setting.
  • Appraisal Committee

    An independent committee that develops NICE's guidance on using drugs or treatments in the NHS (called technology appraisal guidance). It is made up of healthcare professionals and NHS managers, researchers, lay representatives, and people who work for drug companies and medical equipment manufacturers.
  • Appraisal consultation document

    The Appraisal Committee's draft guidance on using a drug (or group of drugs) or treatment in the NHS (called technology appraisal guidance). The manufacturer and organisations who have been invited as consultees and commentators can comment on this draft guidance.
  • Appraisal of evidence

    Formal assessment of the quality of research evidence and its relevance to the topic being considered. It is assessed according to predetermined criteria.
  • Arm (of a clinical study)

    Subsection of participants within a study who receive a particular intervention (for example, the usual care arm).
  • Assessment Group

    An independent group of researchers commissioned by NICE to review the evidence on a group of treatments, for a multiple technology appraisal. The Assessment Group includes researchers who assess the quality of studies on the treatments, and health economists who look at whether the treatments are good value for money. The Appraisal Committee bases its discussions on the assessment report produced by the Assessment Group.
  • Assessment report

    A review of the evidence about how well health technologies work and how much value for money they present. The assessment report forms the basis of the Appraisal Committee's discussions. The assessment report is written by an Assessment Group. Assessment reports are produced for treatments being assessed using the multiple technology appraisal process.
  • Association

    Statistical relationship between 2 or more events, characteristics or other variables. The relationship may or may not be causal.
  • Audit

    A systematic review of a practice, process or performance to establish how well it meets predetermined criteria. The procedure includes identifying problems, developing solutions, making changes to practice, and then reviewing the whole operation or service again. For example, audit may be carried out on a specific service (such as stop smoking services), to check whether it complies with laws, regulations or policies. See clinical audit.
  • Audit Committee

    A subcommittee of NICE's board that keeps a check on NICE's finances and other aspects of the way the organisation is run.
  • Audit trail

    Records of action to assess practice against standards. Also a record of actions (for example, changes to draft recommendations) so that the reasons are apparent to a third party.