Screening – Prevention That Saves Lives


Most of you will by now have heard the phrase ‘Prevention is better than cure.’ It’s a saying I have adopted as something of a mantra as a doctor. We’ve seen a huge rise in interest in lifestyle behaviours that affect our health – diet and nutrition, physical activity, sleep, stress, social connection, to name but a few. These are probably the most popular behaviours we see discussed in the social media world, and yes, they are extremely important. But what is equally important is that we do not forget the other lifestyle factors that are crucial to optimising our short and long-term health. These include for example sexual health, vaccination/immunisation, alcohol intake, smoking, and the topic of this article – screening. If you haven’t heard of or learnt much about screening to date (this will depend on your age, gender and socio-economic and cultural background), fear not, because I’m going to share with you what screening is, why it’s important as a preventive medicine concept, and how it applies to our day to day life for physicians and patients alike.

What IS Screening?

Screening in the context of medicine and health care is defined as – the application of a test that detects an unsuspected disease in people that are not showing any symptoms. This means that screening tests are NOT diagnostic tests. Repeat that sentence again to yourself, because many patients fear going for their screening test, be it a mammogram or a cervical smear, as they understand these tests to be diagnostic of a certain disease if positive. Screening tests are performed on people who have no symptoms of, but who are at risk for developing, the disease in question (e.g. breast cancer, cervical cancer, etc). In contrast, a diagnostic test is performed on a patient who HAS signs or symptoms of a disease. This difference is crucial to understand, and knowing the difference between screening and diagnostic tests can help remove a lot of the anxiety surrounding attending for a screening test. Screening tests are provided for free in Ireland.

Why Do Screening At All?

The main reason we have screening programmes is because the evidence tells us that these tests reduce both morbidity (i.e. physical and psychological harm) and mortality (i.e. deaths) from the disease in question, and ultimately improve health outcomes. A screening programme will only be introduced if the EVIDENCE from research performed nationally and internationally tells us these reductions are proven, and importantly, that the benefits of screening certain subgroups of the population for disease outweigh the potential harms. Examples of potential harms from screening programmes include false negative and false positive results of screening tests (because no test can be perfect, these will essentially always arise to a lesser or greater extent) in particular. False positive results (i.e. a healthy person tests positive for disease) can lead to anxiety, unnecessary further investigations and possible complications from further investigations, while false negative results (i.e. a person with pre-clinical or clinical disease incorrectly tests negative) can lead to false reassurance and missed opportunities for further investigation and earlier treatment or management of disease. Our screening programmes operate on a ‘call-recall’ type of system, whereby those eligible for screening are invited to attend, and clinical services are made available for further investigation and possible diagnosis if a person is found, based on their screening test, to be at risk of having or developing the disease in question. For example, if a woman has her mammogram performed as part of our BreastCheck programme and some changes are seen on it, she will be called back for further assessment, investigation and review, to clarify whether these changes are something to be concerned about or not.

Screening programmes have to fit a strict number of criteria – for the disease, the test and the programme itself. I’m not going to describe them all here, but suffice to say that a LOT of multi-disciplinary consultation, research and planning goes into introducing a screening programme. For example, during my Masters we learnt about the Jungner and Wilson criteria which must be satisfied before a screening programme is introduced (see below):

In addition, the Irish National Cancer Strategy launched in 2006 (an updated strategy has been recently launched since then) also detailed specific criteria (the National Cancer Forum criteria for decisions on the introduction of
population-based screening) which must be fulfilled for the screening test, the programme itself, and the actual condition, before a programme can be introduced (see below). Some of these overlap with Jungner and Wilson but they are more comprehensive. As you can see, a lot of consideration for every aspect of the programme and the impact it will have on the health of the population is considered before a programme is introduced:



What Do We Screen For?

Cancer Screening

In Ireland, we screen for breast, cervical and colorectal cancer – with our programmes BreastCheck, CervicalCheck and BowelScreen. Screening is a form of what’s called secondary prevention – an example of primary prevention would be the HPV vaccine for cervical cancer, whereas cervical screening aims to detect pre-cancerous cell changes due to HPV. It’s really REALLY important to engage with your screening appointments whatever age you are! Check out the National Screening Service to know the ages and intervals of screening programmes in Ireland – I’ve very briefly summarised each below, but I would encourage you to hit the click-able links I’ve created to each programme, as these Health Service Executive websites will tell you much more detail on our screening programmes, the benefits and possible risks, follow-up investigations if required, and further emphasise why attending for your screening is so important.


There are other conditions we screen for in Ireland, for example:

  • Patients with type 1 or 2 diabetes over the age of 12 are invited to receive an annual screen of the back of their eye (a part called the retina) to screen for any changes related to their diabetes – check out Diabetic RetinaScreen for more information.
  • Newborn screening – Newborns in Ireland have both bloodspot (which tests for a range of important conditions) and hearing screening performed shortly after birth (you can read more on these tests here).
  • Opportunistic screening – for example, a GP might screen an older male or female with heart disease risk factors (e.g. alcohol intake, smoking history, family history) for other relevant risk factors by taking their blood pressure and checking their cholesterol and blood sugars.
  • Antenatal screening – screening for certain diseases in the early stages of pregnancy.

I hope you found this post useful – if you’d like to see more on this topic let me know! There are other statistical specifics I could have gone into in terms of the screening tests themselves, but really what I want you guys to take from this post is the basics of what screening is, why it is important, and what programmes we have in place in Ireland. As always, let me know what you think of the article here, or on social media – I’m @theirishbalance on Instagram/Twitter/Facebook!

Ciara 🙂 x

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