Population screening programmes – guidance

NHS population screening explained

This guide sets out what NHS population screening is, how it works and its limitations.

Screening is the process of identifying healthy people who may be at increased risk of disease or condition.

The screening provider then offers information, further tests and treatment. This is to reduce associated risks or complications.

Illustration of the screening process

It can be helpful to think of screening like a sieve. In this diagram, a large group of people accept the offer of a screening test.

This diagram explains how screeening works.
This image explains how the screening process can be compared to putting people through a sieve.

The sieve represents the screening test and most people pass through it. This means they are at low risk of having the condition screened for.

The people left in the sieve are at higher risk of having the condition. A further investigation is then offered to them.

Identification through this process can show that they have the condition screened for. The person may need further confirmatory diagnostic tests.

At each stage of the screening process, people can make their own choices about further:

  • tests

  • treatment

  • advice

  • support

Limitations of screening

Ethics of populations screening

Because the NHS invites apparently healthy people for screening, healthcare professionals have to ensure individuals receive:

  • guidance to help make informed choices
  • support throughout the screening process

Screening expectations

The public needs to have realistic expectations of what a screening programme does.

Screening can:

  • save lives or improve quality of life through early risk identification

  • reduce the risk of developing a serious condition or its complications

Screening does not guarantee protection. Receiving a low risk result does not prevent the person from developing the condition at a later date.

In any screening programme there are a false positive and false negative results:

  • false positive: wrongly reported as having the condition

  • false negative: wrongly reported as not having the condition

Screening videos

These 4 videos explain concepts central to the NHS population screening:

The basics of screening

the basics of screening

Prevalence

prevalence

Sensitivity and specificity

sensitivity and specificity

False positives and false negatives

false positives and false negatives

Other resources

The Making Sense of Screening guide published by Sense About Science provides a good introduction to the benefits and harms of screening and addresses a number of common misconceptions.

The Health Knowledge interactive learning module can help you to gain an in-depth understanding of screening.