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What is screening?

Screening is the process of identifying apparently healthy people who may be at increased risk of a disease or condition. The NHS offers screening to defined groups of people, such as newborn babies or 65 year-old men. It is only offered if evidence shows that it will do more good than harm to most people.  The screening provider (often an NHS Trust) will offer information, the screening test and any further tests and treatment. Screening can prevent illness, keep people healthier or reduce the risks or complications of the condition.

For example, newborn hearing screening aims to identify babies with hearing loss early enough to provide skilled support for communication and language development. Screening 65 men for abdominal aortic aneurysms saves lives by enabling them to have surgery to prevent their aorta bursting.

Antenatal screening can be to offer reproductive choice and information rather than treatment.

‘Population screening’ is a term used by Public Health England (PHE) to differentiate the national screening programmes, which offer screening to large populations of people, from other types of screening (such as MRSA screening on admission to hospital).

GOV.UK has lots of information about population screening for professionals. NHS Choices provides information for the public.

 

UK National Screening Committee

The UK National Screening Committee (UK NSC) advises ministers and the NHS in the 4 UK countries about all aspects of population screening and supports implementation of screening programmes.

It reviews conditions against its evidence review criteria to determine whether to recommend screening. It only recommends screening if:

  • there is an accurate and acceptable screening test

  • treatment and advice is available for people who are found to have the condition

  • the screening programme would do more good than harm to those who are screened

Ministers in each UK country then decide, based on the UK NSC recommendation, whether to implement a new population screening programme for that condition.

Sometimes the UK NSC can recommend stopping screening for a condition if the evidence suggests it is no longer effective as a screening programme. This happened in 2016 with screening for rubella susceptibility.

  

Leading and providing the national screening programmes

PHE leads the national screening programmes in England. This means it:

The NHS commissions and provides local screening services that meet the national service specifications developed jointly by PHE and NHS England.

Screening as a pathway

Screening is not just a test. A test on its own will not improve outcomes. All parts of a care pathway need to be in place for screening to be effective. The main steps are:

  • identifying the individuals eligible for screening

  • inviting eligible individuals for screening

  • giving information to enable people to make an informed choice

  • carrying out the screening test

  • acting on screening results: referral, diagnosis, intervention and treatment

  • providing support and follow-up

This process is the screening pathway, managed as part of a screening programme. A screening programme supports people throughout the process, from inviting people for screening to referring anyone found to have a particular condition for treatment and advice.

 

Screening as a sieve

It can be helpful to think of screening like a sieve. The screening sieve will catch some people and allow others to pass through. A screening test catches people who are at higher risk of a condition. Everyone picked up in the sieve will go on for more testing to determine if they have the condition and need treatment. The people who pass through the sieve are those at lower risk of having the target condition and they are not offered further investigations.

Screening tests must be ‘sensitive’. The sensitivity of the screening process is the measure of its ability to catch those people who are at risk of having the target condition.

The screening process must also be ‘specific’. The specificity of the screening process is its ability not to refer individuals who do not have the target condition.

Sometimes people will get stuck in the sieve who will turn out not to be at risk. These are ‘false positive’ results.

Others will pass through the sieve despite being at risk. These missed cases are ‘false negative’ results.

No screening test is perfect. This means they don’t have 100% sensitivity or specificity.

 

Personalised informed choice

Screening is a choice and it is important that people are given unbiased, balanced information, in a timely manner and in a format they can understand to help them make that choice. While all screening programmes do good at a population level, some can cause harm to an individual. For instance, a man found by screening to have an abdominal aortic aneurysm may suffer side effects from surgery.

The information should enable them to make decisions which are right for them and their particular beliefs and values.

Obtaining consent for screening is a professional obligation and a matter of respect between health professionals and individual. The health professional carrying out the screening is ultimately responsible for ensuring that the individual has an understanding of the procedure and has given consent. Individuals should never be criticised for declining screening.

PHE promotes ‘personalised informed choice’. This is:

‘A decision made to accept or decline a screening test based on access to accurate, up-to-date information on:

  • the condition being screened for

  • the testing process

  • potential outcomes

There should also be the opportunity to reflect on what the test and its results might mean to them as an individual.’

 

Keeping up to date

The best way to get the latest news and updates on population screening in England is through the PHE Screening blog and Twitter feed.

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