By Dr Alan Smith, Consultant in Public Health Medicine, National Screening Service
On World Health Day 2026 (7 April), the theme ‘Together for health. Stand with science’ highlights the role of science in protecting and improving health. Population screening is one of the clearest examples of science in action, where decades of research are translated into real benefits for people every day.
What it means to stand with science
In healthcare, ‘standing with science’ means using the best available evidence to guide decisions that affect people’s health.
Building that evidence means asking many science-based questions, including:
- what works?
- what helps people live longer or healthier lives?
- what are the risks and how can we minimise them?
Population screening is built on responding to these types of questions with science-led answers. It is one of the ways we turn scientific knowledge into real-world action.
Screening: science in action
Screening programmes are designed to find disease early, or to prevent it altogether, in people who do not have symptoms of the disease been screened for.
Our 4 national screening programmes – BowelScreen, BreastCheck, CervicalCheck and Diabetic RetinaScreen - invite people at certain ages to take part in screening that is free, quality-assured and evidence-based.
Behind every invitation is a goal to reduce illness and save lives through prevention and early detection.
Screening: built on evidence
Population screening programmes are developed over many years, based on strong scientific evidence.
This includes:
- randomised controlled trials
- systematic reviews of international research
- health technology assessments
- epidemiological modelling
- clinical expertise.
Together, this evidence helps us understand not just whether screening works, but how it works best.
How screening decisions are made
Offering screening to a population is a careful and structured decision. While it’s about preventing disease or finding it earlier, it is also about weighing both the benefits and the possible harms of screening.
Benefits can include:
- preventing disease
- earlier diagnosis
- better treatment outcomes.
Possible harms can include:
- false positives (when a test suggests something is wrong when it is not)
- false negatives (when a test suggests everything is normal when something is wrong)
- overdiagnosis (finding changes that would not have caused harm)
- unnecessary follow-up tests and anxiety.
Screening is only offered when there is clear evidence that the benefits outweigh the possible harms. These decisions are made through structured processes, guided by experts and regularly reviewed as new evidence emerges.
One of the most common questions about screening is why it is offered at certain ages or at set intervals. The answer is that these decisions are based on evidence about when screening is most effective.
For example:
- the age groups invited are those most likely to benefit
- the time between tests is based on how quickly changes are likely to develop
- the type of test used is chosen for its accuracy and reliability.
Every part of a screening programme, from the invitation letter to the test itself, is carefully designed and based on evidence.
Evidence matters in a world of mixed messages
People today are exposed to a wide range of information about health, not all of it accurate.
Screening programmes are grounded in robust, independently reviewed evidence. They are developed through transparent processes and are continually improved and updated as new research becomes available.
This strong evidence base helps people make informed decisions about their health.
Screening keeps evolving
Science does not stand still, and neither does screening.
Our screening programmes continue to evolve as new evidence and technologies emerge.
For example:
- we moved to primary HPV testing in CervicalCheck in 2020 because the evidence showed this is a better test with improved outcomes for women
- we’re expanding the eligible age range for BowelScreen in carefully managed stages based on evidence-based recommendations
- we’re part of an international study - the Microb-AI-ome project – exploring whether analysing the gut microbiome using AI can help find early signs of bowel cancer more accurately, and reduce the number of colonoscopies needed as a screening tool
These changes reflect our commitment to continuous improvement. We’re making screening more effective, more accessible and more responsive to people’s needs.
We can eliminate cervical cancer because of science
That heading itself is made possible because of the decades of work by researchers, public health professionals and clinicians.
Because of science, we know that the human papillomavirus (HPV) causes most cases of cervical cancer. We have a vaccine to protect us from the high-risk types of HPV – it’s our first line of protection against cervical cancer. And cervical screening is a test for HPV first, so we can find those people who are most at risk and stop cervical cancer before it starts, or find it earlier when it can be easier to treat and cure.
We’re on track to eliminate cervical cancer in Ireland by 2040.
The next chapter: AI and the future of screening
Artificial intelligence (AI) is the next step in the evolution of science-led screening.
AI has the potential to:
- support clinicians in reading screening tests
- increase efficiency in screening
- support earlier detection of disease
- reduce unnecessary follow-ups for people who take part in screening
- help services plan for growing demand as our population increases.
Importantly, AI will support – not replace - clinical expertise. We have started to implement an AI programme in the National Screening Service. It is another tool that will help us use evidence more effectively to improve outcomes for people.
Choosing screening is choosing science
When you take part in screening, you are engaging with a healthcare system built on decades of research, evidence and clinical expertise.
You are choosing an approach to health that is:
- informed by science
- focused on prevention and earlier diagnosis
- designed to achieve the best possible outcomes.
For the more than one million people who take part in our national screening programmes each year, it is something practical, personal and potentially life-changing. That is screening: science made real.
On World Health Day, stand with science by engaging with evidence, facts and science-based guidance to protect your health. Choose screening.