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Healthcare providers regularly consult documents called guidelines when determining the best way to treat a patient.

Occasionally – as is expected with Monday’s announcement of new guidelines about treating high blood pressure – they can make big news.

But what exactly are guidelines? Why are they so important? And how are they made?

Guidelines are documents that help doctors understand the best ways to diagnose, treat and even prevent diseases and conditions. Guideline recommendations are based on the strongest available scientific evidence and a rigorous approach.

The creation of a guideline is a rigorous process because careful scientific study is at the heart of every guideline. When the American Heart Association develops guidelines, either alone or in conjunction with other organizations, it all starts with an oversight committee made up of volunteer experts. This group identifies the topic and the major questions to be addressed, and appoints the writing committee.

The writing committee is usually made up of about 15 scientific and medical experts. They’re unpaid volunteers with varying backgrounds to ensure numerous viewpoints.

“This is a task performed by people who are passionately committed to making sure the very latest and very best evidence is made available to healthcare providers,” said Elliott Antman, M.D., a former AHA president who chaired a guideline writing committee in 2004 that helped speed the effective treatment of a deadly type of heart attack.

It’s important to make sure that the writing committee is not influenced by pharmaceutical companies, device manufacturers or related industries that could lead to bias in any guideline recommendation. There are rules in place governing this.

However, for some guidelines, it may be beneficial to the process to include a minority of individuals with some industry relationships because of their expertise, said Antman, associate dean for clinical/translational research at Harvard Medical School and senior physician in the cardiovascular division of Brigham and Women’s Hospital in Boston. Antman added that those individuals are not allowed to vote on recommendations relevant to their industry relationships.

Once appointed, the writing panel starts gathering published research and analyzing it carefully. The experts take care to include the most important and scientifically rigorous research – and to exclude research that doesn’t meet that standard.

After discussion, debate and voting, the committee members agree on what to recommend. Next, they decide how to prioritize recommendations. The recommendations are broken down by “class” and “level.” Class refers to how likely a recommendation is to help a patient while keeping risks in mind. Level of evidence rates the type, amount and consistency of research, on a scale from A to C.

So, for example, the strongest recommendation is Class IA, meaning it’s the most helpful advice based on the strongest kind of research.

Once the committee arrives at recommendations, the peer-review process begins. Recommendations are sent out to numerous experts to review, check, object, comment or question. In the guidelines Antman chaired, for example, 93 people outside the writing committee provided feedback, he said.

“It is not unusual to respond to several hundred or a thousand comments,” said Alice Jacobs, M.D., a former AHA president who has served on writing committees and for three years chaired the committee that oversees all joint guidelines created by the AHA and the American College of Cardiology.

“When published, the document has been vetted through much of the academic and clinical community with expertise in the topic,” said Jacobs, vice chair for clinical affairs in the Department of Medicine at Boston Medical Center and a professor of medicine at Boston University School of Medicine.

The American Heart Association has published medical information and guidelines since its 1926 publication, “A Nomenclature for Cardiac Diagnosis,” which helped doctors diagnose heart disease. Since then, the organization has created guidelines covering a wide variety of topics related to heart disease and stroke.

The association has created numerous guidelines with the American College of Cardiology. The two first worked together on 1984 guidelines about pacemakers – a request that came from the federal government. Since then, the two organizations have created guidelines addressing 20 different cardiovascular disease topics.

In 2013, the federal government’s National Heart, Blood, and Lung Institute asked the two organizations to officially lead the process for an important group of cardiovascular disease guidelines, those focused on prevention.

One challenge of creating guidelines is that the treatments are based on averages: what will help the most patients with the fewest side effects. But there’s no such thing as an average patient, Antman said. Thus, the patient’s own healthcare provider needs to apply clinical judgment to how a guideline applies to that individual.

Future guidelines will incorporate findings from precision medicine where information such as a person’s genetic makeup will be used to target specific individuals, Antman said. Rather than developing recommendations for the average person, the “personalized” approach to medicine means cardiovascular treatments will be even more precise in the future, Antman said.

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