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 have an increased chance of a disease or condition.
The screening provider then offers information, further tests and treatment. This is to reduce associated problems 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.
The sieve represents the screening test and most people pass through it. This means they have a low chance of having the condition screened for.
The people left in the sieve have a higher chance 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:
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
The public needs to have realistic expectations of what a screening programme does.
save lives or improve quality of life through early identification of a condition
reduce the chance of developing a serious condition or its complications
Screening does not guarantee protection. Receiving a low chance result does not prevent the person from developing the condition at a later date.
In any screening programme there are false positive and false negative results:
false positive: wrongly reported as having the condition
false negative: wrongly reported as not having the condition
These 4 videos explain concepts relating to population screening:
The basics of screening
Sensitivity and specificity
False positives and false negatives
The Health Knowledge interactive learning module can help you to gain an in-depth understanding of screening.