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.

  • 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 ('commercial in confidence') or the academic interests of a research or professional organisation ('academic in confidence').
  • In depth interview

    A qualitative research technique. It is a face-to-face conversation between a researcher and a respondent with the purpose of exploring issues or topics in detail. It does not use pre-set questions, but is shaped by a defined set of topics or issues.
  • Incidence

    The number of new cases of a disease among a certain group of people during a specific period of time. It is different from prevalence.

  • Incremental analysis

    The analysis of additional costs and additional clinical outcomes with different interventions.
  • Incremental cost

    The extra cost linked to using 1 test or treatment rather than another. Or the additional cost of doing a test or providing a treatment more frequently.
  • Incremental cost-effectiveness ratio (ICER)

    The difference in the change in mean costs in the population of interest divided by the difference in the change in mean outcomes in the population of interest.

  • Index test

    The test in a study that is being compared with the best available test (the reference standard).

  • Indicator

    A statistic or marker that has been chosen to monitor health or service activity. For example, an indicator might be the number of women attending for breast cancer screening or the number of deaths from coronary heart disease in a defined population.
  • Indirect comparison

    An analysis that compares interventions that have not been compared directly in a head-to-head, randomised trial.
  • Information bias

    This can affect all types of research study. It can be caused by questionnaires that have difficult or biased questions, observer or interviewer errors (for example, lack of blinding), response errors (for example, if patients are aware of the treatment they are having) or measurement error (for example, a faulty machine).

  • Information for the public

    A summary of a piece of NICE guidance in everyday language for patients, carers and the general public.
  • Information specialists

    Specialists with expertise in information retrieval, based either at NICE or in a Development Centre, who provide information to support the committees developing guidance.

  • Intention-to-treat analysis (ITT)

    An assessment of the people taking part in a trial, based on the group they were initially (and randomly) allocated to. This is regardless of whether or not they dropped out, fully adhered to the treatment or switched to an alternative treatment. ITT analyses are often used to assess clinical effectiveness because they mirror actual practice, when not everyone adheres to the treatment, and the treatment people have may be changed according to how their condition responds to it. Studies of drug treatments often use a modified ITT analysis, which includes only the people who have taken at least 1 dose of a study drug.

  • Internal validity

    See Validity

  • Intervention

    In medical terms this could be a drug treatment, surgical procedure, diagnostic test or psychological therapy. Examples of public health interventions could include action to help someone to be physically active or to eat a more healthy diet. Examples of social care interventions could include safeguarding or support for carers.

  • Interventional procedures advisory committee

    The independent committee that advises NICE on whether an interventional procedure is safe enough and works well enough to be used in the NHS. The committee comprises clinicians who carry out interventional procedures, people who are familiar with the issues affecting patients, carers and trusts, experts in regulation and in the evaluation of healthcare and a representative from the medical technologies industry.

  • Interventional procedures consultation document

    The interventional procedures advisory committee's preliminary recommendations about whether a procedure is safe enough and works well enough to be used in the NHS. The equipment manufacturer and organisations registered as consultees can comment on the draft guidance during a consultation that lasts 4 weeks.

  • Interventional procedures guidance

    NICE's guidance about whether an interventional procedure is safe enough and works well enough to be used in the NHS. An interventional procedure is a test, treatment or surgery that involves a cut or puncture of the skin, using an endoscope to look inside the body, or energy sources such as X-rays, heat or ultrasound.
  • Interventional Procedures Programme

    Assesses the efficacy and safety of interventional procedures used for treatment or diagnosis. It can assess procedures that involve a cut or puncture of the skin, use an endoscope to look inside the body, or use energy sources such as X-rays, heat or ultrasound.