Finding the best way to measure the cost-effectiveness and health impact of preventive interventions could help secure more investment, write Julian Le Grand and Robert Sherriff

Earlier this month, in his first major speech on the NHS, prime minister Gordon Brown announced the launch of a new national screening programme and confirmed the government's commitment to the importance of prevention.

This reaffirmed earlier commitments in the white paper Our Health, Our Care, Our Say and in the Our NHS, Our Future interim report from junior health minister Lord Darzi, which highlighted the "need to pursue evidence-based interventions that support people to make healthy choices and prevent ill health".

There is now a broad political consensus on prevention. Given this political environment, it places an important responsibility on all those interested in improving health to be able to provide clear advice to policy makers on which preventive interventions should be next in line for government support.

To this end government has set up Health England, an independent body with the twin tasks of prioritising preventive interventions and identifying ways of incentivising commissioners and others to support these interventions.

There has been considerable debate over the most appropriate way to make economic evaluations of public health interventions. This has focused on how best to determine cost-effectiveness. However, we at Health England believe that just as important as cost-effectiveness is the overall health benefit to the population of an intervention. In other words, there is a need to ensure that the policies prioritised have the greatest beneficial impact.

The Health Foundation's Quest for Quality and Improved Performance initiative has highlighted the importance of measuring the impact of health policy interventions on target populations. LSE professor of management science Gwyn Bevan and colleagues have described the three elements of the burden of disease: the burden avoided by current care, the burden avoidable by improving care and the unavoidable burden. Knowledge of the burden avoidable by improving care is a key component in helping to determine priorities for both treatment and prevention.

We also believe that other factors such as overall affordability and time taken to see the benefit need to be taken into account when deciding on priorities for prevention.

Top ranking

Is all this discussion about setting priorities for prevention just policy pie in the sky? We think not, for a national commission on prevention priorities in the US has developed a methodology for setting priorities among effective preventive services. After applying the methodology it published a ranking of primary and secondary preventive services, including immunisations, screening tests, counselling and preventive medications offered to asymptomatic individuals.

These interventions have previously been determined as effective by either the independent US preventive services task force or the advisory committee on immunisation practices. But how do they stack up against each other when compared from a policy maker's viewpoint, which takes into account the total morbidity and mortality which could be prevented in the population?

The prevention priorities commission based its rankings on the clinically preventable burden, which measures a service's population health impact and cost-effectiveness, which in turn measures the service's economic value. Each service was given one to five points on each of the two measures, for a total score ranging from two to 10. The highest ranking interventions can be seen in the table below.

The study provided additional information on unmet opportunities and the number of total quality-adjusted life years that could be saved where the percentage of people receiving selected interventions increased to 90 per cent.

Health England has commissioned an assessment of the general usability of the results and methodology of the US study in an English setting from Brunel University. While the US study focused exclusively on clinical preventive interventions, our intention is to apply a similar methodology to longer term community preventive interventions, such as approaches to increasing physical activity.

Focusing effort

We believe an approach that prioritises on the basis of population health impact and cost-effectiveness will be of importance to national policy makers. This approach is of relevance to busy commissioners in the NHS and local government, as it will help to identify where to apply most effort in order to achieve most population benefit. A decision to implement a preventive programme at local level comes with an opportunity cost, not just in terms of finances but also in terms of staff time.

For instance, public health and clinical staff implementing a new preventive programme will have less time available for focusing on other preventive programmes. Ensuring that time is spent on achieving most local population health benefit seems a reasonable expectation.

Our aim is to develop a model for prioritisation to be used by Health England in order to give advice on which preventive interventions should be the priorities for investment. We hope to stimulate an open debate to ensure the public and professionals are engaged in the process.

It is important to ensure we know what can be achieved with modest or major investments. Knowing how much population health benefit can be achieved for an investment of£50,000 or£500,000 should help to stimulate debates both at national policy level and in NHS boardrooms across the country. This would be a major step towards shifting the investment focus to preventive interventions. We recognise that this must be accompanied by incentives for ensuring long-term financial investment in prevention. Health England is preparing a document to start a debate in this area.

We congratulate the commission for gathering this research and for publishing the rankings of preventive interventions. Health England is trying to do something similar, only at an even more ambitious level for England: to prioritise not only clinical but also community interventions. While we are not saying the methodology we are highlighting is perfect, we do believe it represents a major step forward and shows us the importance of considering preventive interventions both in terms of cost-effectiveness and population impact.

How to decide on priorities for prevention

  • What is the burden of disability and disease?

  • How much of this burden is preventable?

  • Which of the interventions is good value?

  • How much population health benefit will interventions deliver?

  • Is full implementation of the intervention affordable?

  • How much population health benefit can we get for£50,000 or£500,000?

  • How long must we wait to see the population health benefit? Five, 10 or 20 years?

Top preventive services for the US population

Clinical preventive servicesPreventable burden (out of 5) Cost-effectiveness (out of 5)Total
Discuss daily aspirin use - men 40-plus, women 50-plus5510
Childhood immunisations5510
Smoking cessation advice and help to quit - adults5510
Alcohol screening and brief counselling - adults459
Colorectal cancer screening - adults 50-plus448

Source: Journal of Preventive Medicine, 2006

Find out more

Health England

Estimating health and productivity gains in England

US commission on prevention priorities

Rankings of preventive services for the US population