Screening: introduction

Public information on screening programmes are provided by NHS Inform. These pages are for a professional audience and public health intelligence in relation to screening programmes.

The underlying concept of screening is that in some circumstances the early detection of risk factors or undiagnosed disease can be associated with health benefits. Screening is designed to identify conditions early, before symptoms are present or a diagnosis is made.

Screening has been defined as:

"a public health service in which members of a defined population, who do not necessarily perceive they are at risk of, or are already affected by a disease or its complications, are asked a question or offered a test, to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications" (UK National Screening Committee).

Or more simply to refer to:

"the use of simple tests across an apparently healthy population in order to identify individuals who have risk factors or early stages of disease, but do not yet have symptoms" (World Health Organization).

Screening differs to diagnosis testing (see HealthKnowledge) as it aims to detect early disease or risk factors for disease in apparently healthy individuals, while a diagnostic test seeks to establish the presence (or absence) of disease as a basis for treatment decisions in symptomatic or screen positive individuals.

When is screening appropriate?

Decisions on whether a screening programme should be introduced are based on the ten criteria described by Wilson and Jungner in 1968 (6Mb). These can be grouped as follows:

  • The disease or condition:
  1. Should be an important health problem.
  2. The natural history of the condition, including development from latent to declared disease, should be adequately understood.
  3. There should be a recognisable latent or early symptomatic stage.
  • The screening test:
  1. There should be a suitable test or examination.
  2. The test should be acceptable to the population.
  3. Case-finding should be a continuing process and not a 'once and for all' project.
  • The diagnosis/treatment:
  1. There should be an agreed policy on whom to treat as patients.
  2. There should be an accepted treatment for patients with recognized disease.
  3. Facilities for diagnosis and treatment should be available.
  • The programme overall:
  1. The cost of case-finding (including diagnosis and treatment of patients diagnosed) should be economically balanced in relation to possible expenditure on medical care as a whole.

The criteria have been expanded on for appraising the variability, effectiveness and appropriateness of a screening programme by the UK National Screening Committee. The Scottish Government advocates that the criteria set by the UK National Screening Committee should ideally be met before screening for a condition is initiated.

Other similar criteria have been proposed (see for example Harris et al (2011)) and there are debates about widening the criteria further with, for example, the sequencing of the human genome and identification of many more genetic conditions through their genetic code, see Andermann et al (2008) .

Other developments since the publication of the Wilson-Jungner criteria include:

  • Increased screening for risk factors (eg raised glucose or cardiovascular risk scores) rather than for disease.
  • Increased use of screening under other labels such as “case finding”, “disease awareness” campaigns or health checks.
  • Controversies about breast and prostate screening have increased the awareness of the need for high quality trials to support new screening programmes.
  • Increased awareness of the potential for harm as well as concerns that those participating in screening have not been fully informed of possible harms.

Current screening programmes in Scotland

The current screening programmes in Scotland are:

  • Cancer
  1. Bowel - men and women aged between 50 and 74 years, every 2 years.
  2. Breast - eligible women aged between 50 and 70 years, every three years.
  3. Cervical - eligible women aged between 25 and 49 years every three years and eligible women aged between 50 and 64 years every five years.
  • Abdominal Aortic Aneurysms (AAA) – men aged 65 years old, invited only once.
  • Diabetic retinopathy – condition-based screening programme specific for diabetics aged 12 years and over.
  • Newborn screening for:
  1. Phenylketonuria.
  2. Congenital Hypothyroidism.
  3. Cystic Fibrosis.
  4. Medium Chain Acyl-CoA Dehydrogenase Deficiency.
  5. Sickle Cell Disorder.
  6. The Universal Newborn Hearing Screening.
  • Pregnancy screening:
  1. Sickle Cell Disorder and Thalassaemia (Haemoglobinopathies).
  2. Down's Syndrome.
  3. Neural tube defect.
  4. Human Immunodeficiency Virus.
  5. Hepatitis B.
  6. Syphilis.

For further information see the following, which also contain many public information publications:

Other screening

Other forms of screening are also undertaken in Scotland:

  • Blood and tissue donations – automatic testing for various communicable diseases such as:
  1. Human Immunodeficiency Virus.
  2. Hepatitis B and C.
  3. Human T-cell lymphotropic virus.
  4. Syphilis.

And some discretionary testing, for example, for:

  1. Malaria.
  2. West Nile Virus.
  3. Trypanosoma cruzi.

Tissue donations are also tested for bacterial and fungal contamination:

  • Genetic screening.

For further information see: