How is the quality of medical research graded? What is evidence-based medicine?

When WE DOCTORS WANT to know how well a medical treatment is likely to work, they often follow guidelines that have been drawn up from the best available medical research evidence.

Evidence-based medicine is a term used for this way of practising - doctors looking at the research to help with treatment decisions, rather than relying on judgement, experience and medical TRAINING alone.

Not all medical research evidence offers robust guidance for this kind of clinical decision-making though, and that is where grading comes in.

Grading the reliability of all the studies that add to the sum of knowledge about a particular treatment choice enables the best recommendations to be made in clinical guidelines.

Who grades medical research evidence?

Making decisions about what exactly is the best available evidence for medical intervention is the job of the expert bodies that produce the clinical guidelines taken up by health care providers and doctors. Just some of these organizations include:

• A wide range in the US, among them the American Thoracic Society, the Society for Critical Care Medicine, the University of Pennsylvania Health System Center for Evidence-Based Practice, and UpToDate
• Widely respected international medical bodies such as the World Health Organization (WHO), The Cochrane Collaboration, and the BMJ.

The examples picked out above, among numerous others, use the same system of grading, known simply as the 'GRADE system' - see below for more detail.

Grades of evidence in medical research are drawn from ratings of quality and importance.

When clinical guidelines are produced by medical bodies, they are usually endorsed by panels of leading doctors from the particular field in question.

What these expert panels sign off against is a set of recommendations reached after a thorough review of all the research studies. 

Effectively, the people who make recommendations about the BEST HEALTH CARE programs and medical treatments have gone through each of these pieces of medical research and given them approval ratings.

This way, the best medical advice issued to doctors is transparent about the extent to which it is based on good evidence. The stronger the evidence, the more influential the guidance will be for doctors seeking high levels of confidence in the treatments they offer.

Fast facts on medical research grading

Here are some key points about grading of medical research evidence. More detail and supporting information is in the body of this article.

• Clinical guidelines tell doctors what the best treatments are, based on the latest and most reliable research.
• The body of medical evidence for benefits and harms from a particular treatment includes a variety of study types, not all of which are appropriate to clinical decision-making.
• Some studies can be plainly wrong or misleading. This could be because of poor scientific design, for example.
• The concern of evidence-based medicine is to use the best research available, and this is done by grading the individual studies against sets of criteria that measure their quality and importance.
• Study design methods to investigate a research question fall into a range of grades representing poor to high quality.
• The grade of research offers an indication of the strength of a recommendation.
• The recommendations of clinical guidelines may be based on good evidence, but they can be limited in how well they can be APPLIED to the everyday clinical decisions of doctors helping individual patients.

How are medical research studies graded?

The GRADE system, widely used in the US and internationally, is one example of how ratings are set when reviewing the strength of medical research evidence.

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The GRADE system is one example of how ratings are set when reviewing the strength of medical research evidence. Rating are graded from "very low" to "high."

It follows the idea that good scientific study design gives strong medical evidence, and the design keeps the rating of studies to three simple grades:

• High-grade evidence - randomized controlled trials (RCTs) and systematic reviews of RCTs
• Low - observational studies
• Very low - any other evidence.

If you would like to understand why these different study types produce varying standards of evidence, use the following complete hierarchy.

It is listed in order of increasing robustness of scientific study design, and there arearticles offering further easy-to-follow detail.

• Case report
• Case-control study
• Cohort study
• Randomized controlled trial
• Systematic review
• Meta-analysis.

Good medicine is more than just applying scientifically proven advice

There are limitations to applying the conclusions of medical research studies to the MANAGEMENT of individual people with a disease.

Even the highest form of medical evidence has its limitations - find out more about the disadvantages of systematic reviews and why meta-analyses are powerful, but not always practical.

Individual patients are much more complex than the average of hundreds of narrowly defined research participants.

Further, the people volunteering for scientific studies are different from ordinary patients, and the overall care they receive, also differs.

For these reasons and more, clinical guidelines based on evidence-based research are not always applicable, and when they are, it is experienced clinicians bringing context and expertise which we rely on to follow them appropriately. 

Patients' preferences also dictate the real-life implementation of medicine - and patient-centered care has gathered pace in a similar way to evidence-based medicine in the past decade.