What is screening?

It can be helpful to think of screening like a sieve. In the diagram above, a large group of people are invited for the test. The screening test is represented by the sieve. Most people who decide to accept the offer of being screened pass through the sieve. This means they are at low risk of having the condition that the test is looking for. [NHS-UK]

The people left in the sieve are identified as high risk and are therefore offered further investigation. This may mean they have the condition being screened for but further (diagnostic) tests may be needed to confirm.

In antenatal screening, a high risk screening result could mean that the mother, father or the unborn baby has the condition being tested for. Following a high risk result, options may include further tests, treatment, advice and support. In NHS screening programmes, people are given clear information to help them make their own choices at each stage.

‘Screening is a way of finding out if people are at higher risk of a health problem so that early treatment can be offered or information given to help them make informed decisions. Screening is a way of identifying apparently healthy people who may have an increased risk of a particular condition. The (NHS UK) offers a range of screening tests to different sections of the population.

The aim is to offer screen the people who are most likely to benefit from it. For example, some screening tests are only offered to newborn babies, while others such as breast screening and abdominal aortic aneurysm screening are only offered to older people.’ [Ref NHS UK] This will give a very good understanding of what screening is and what are the screening tests that are recommended by the NHS-UK. This may be somewhat different from what the MoH recommends for Sri Lankan citizens. (I will try and get a link to the recommended screening programs by the Ministry). 

‘Very importantly, screening is not for people with symptoms. If you have any symptoms, go to your doctor.’

There are many screening tests offered by private sector laboratories and health care institutions. The UK government advice before you go for a test.  “Private companies offer a wide range of health checks, from simple blood tests and physical examinations to full-body scans and screening for serious conditions like aneurysms or heart failure. Some of the tests offered by private companies are not recommended by the UK NSC because it is not clear that the benefits outweigh the harms. If you’re thinking about paying for any of these checks, it’s worth asking the following questions first.’ Read the full instructions- LINK

Screening pros and cons

People need information about the condition being screened for and the whole screening pathway before deciding whether or not to accept the test. This is because even the best screening test may not be 100% accurate. Tests may not always give clear-cut answers and the results could even be confusing.

False positive results – These suggest you have a problem when in fact you don’t. They can result in further tests and procedures that you don’t need and a lot of unnecessary worry.

False negative results- These miss a problem altogether. You may go away feeling relieved, and brush aside any signs of trouble later on – thinking that everything must be fine.

Balancing benefit with risk- The NHS has thought very carefully about these issues, taking advice from a group of experts called the UK National Screening Committee (UK NSC). We only run screening programs when good evidence shows that the benefits outweigh any risks. Some screening tests are very good and can be useful in preventing or reducing the risk of disease. However, other screening tests can do more harm than good. The NHS does not offer screening when it can do more harm than good.

‘Prevention is better than cure’ makes intuitive sense. Yet there is evidence that some preventive activities are not effective, some are actually harmful. It has been said ‘all screening programs do some harm; some do good as well’.Screening of asymptomatic patients may lead to overdiagnosis, causing needless anxiety, appointments, tests, drugs and even operations, and may leave the patient less healthy as a consequence. Therefore, it is crucial that evidence clearly demonstrates that benefits outweigh those harms for each preventive activity. [Ref – RACGP Red book]. You can download the 9th ed Redbook