Carl Heneghan: Weighing the evidence in health care

Carl Heneghan is Professor of Evidence-Based Medicine at the University of Oxford, and Director of our extensive programme in Evidence-Based Health Care. He is also a practising GP working in urgent care.

His work includes investigating drugs and devices, advising governments on regulatory evidence and working with the media assessing health claims. At the beginning of the Covid-19 outbreak he set up the Oxford COVID Evidence Service website, which provides rapid evidence reviews and data analysis pertaining to the coronavirus pandemic.

What is evidence-based medicine and why is it so hot right now?

Evidence-based medicine (EBM) is the conscientious, explicit and judicious use of current best evidence in making decisions about healthcare. By integrating individual clinical experience and expertise with the best available external research evidence, EBM forms the foundation of effective decision making in healthcare.

The EBM approach requires being aware of the latest evidence, its strengths, weakness and limitations, and sharing these with patients to inform decision making.

Currently it is informing drug treatments such as the use of dexamethasone that improve Covid outcomes and the vaccines which are underpinned by evidence from randomized controlled trials.

Most of us might assume that all medical protocols are based on the best and most recent evidence – is this not the case?

The volume of clinical research outputs has grown substantially over time. Increasingly it is difficult to identify and integrate evidence into informed healthcare due to the sheer volume of evidence published – 75 trials are published every day.

Of the research done and published, much of it is poor quality: many studies are poorly designed and executed. Our job is to sift through the deluge of research and highlight those studies that make a difference to patient care.

Finding high-quality evidence is sometimes not possible as we often find there is a lack of research answering questions that matter to patients and a lack of evidence to support shared decision making.

There are different levels of evidence, from well-designed random controlled studies, down to observational and empirical evidence (‘in my experience…’). Given the time constraints in managing a medical practice, what should your average clinician be looking for?

To save time and focus on the highest level of evidence I recommend focusing on evidence from systematic reviews.

Systematic reviews involve systematically searching for all available evidence, appraising the quality of the included studies, and synthesising the evidence. They contribute to the best available evidence, translating research into practice, and are powerful tools for effective decision making.

Improvements in technology have increased the speed at which data is available, and access to it. Are most medical practices moving towards an evidence-based approach?

Computers and mobile devices provide instant access to vast amounts of evidence, data and useful information for health care professionals. Modern technologies provide earlier access to new information and through the use of clinical decision support systems they can improve decision making for patient care. They also provide easy and timely access to information and enable accurate and complete documentation.

Over the last four decades there has been an increasing trend towards using an evidence-based approach. It is widespread across all disciplines in medicine and surgery.

Further, what we are starting to see is the development of evidence-based policy across many disciplines. For example, there is now a move towards evidence-based policing and evidence-based education amongst other areas of policy.

News headlines sometimes report conflicting claims, based on single studies – how can the average person be better informed in assessing healthcare claims in the news?

framework for helping people learn how to assess treatment claims and make informed choices has been developed that sets out key concepts required to assess unreliable claims, understand whether treatment comparisons are fair and reliable and make informed choices. The framework contains 36 concepts that you can find on the Informed Health Choices site.

Developed by many individuals who have taught, thought about and tried to inform choice, the concepts are organised into three groups, that can help to recognise when a claim about the effects of treatments has an untrustworthy basis; recognise when evidence from comparisons of treatments is trustworthy and when it is not and make well-informed choices about treatments.

I also recommend the Testing Treatments Website as a way to think critically about treatment claims, review treatment options and participate actively in making a decision about a claim.


Carl Heneghan is Professor of Evidence-Based Medicine at the Department of Primary Care Health Sciences at the University of Oxford, Director of the Centre for Evidence-­Based Medicine and Director of Programmes in Evidence-Based Healthcare, and Editor of the Catalogue of Bias, and an NHS General Practitioner working in urgent care. 


Published 23 February 2021