According to a study published this week in the Journal of the American Medical Association nearly half of the treatment guidelines given to cardiologists by the country's leading heart organizations are not based on conclusive research. 

Doctors said the study brings to the forefront the lack of scientific evidence which controls the questions of the complex treatment involved, such as how much aspirin to prescribe as a preventive dosage, and what procedure should be selected in certain cases. The findings emphasize the need to improve the way research is carried out and guidelines are written. 

Dr. Pierluigi Tricoci, a faculty member at Duke Clinical Research Institute in Durham, North Carolina, and the lead author of the study said, "I think it's very eye-opening and I think it should start some serious discussion on how we can improve the research system here and how we can provide useful information to the clinician who every day faces problems with patients."

Research has shown that patients are better off when doctors follow guidelines based on scientific evidence. Sidney Smith of the University of North Carolina-Chapel Hill, an author of the study and an expert on medical guidelines said, "There's no doubt in my mind that the use of evidence-based medicine has improved patient care. The trouble is we need more evidence."

Tricoci and his co-authors went through 53 guidelines including a total of 7,196 recommendations from 1984 to 2008 published by the American College of Cardiology and the American Heart Association. Each recommendation was classified as I, II or III with I being the strongest while the levels of evidence were classified as A, B, or C with A being the strongest. 

The researchers found that in the 16 lists of guidelines that report strongest levels of evidence out of the 2,711 recommendations only 314 or less than 12 % are based on randomized trials and classified as level of evidence A, compared to 1,246, or 48%, that are level of evidence C. Tricoci said, a recommendation based on evidence C "has no evidence to support it, other than anecdotal. The opinion of some expert [about the] so-called standard of care."

Smith said the best evidence comes from studies in which patients are randomly divided into two groups and given different treatments with neither them nor their doctors knowing what treatment they have received. These studies take years to complete and often cannot give the necessary information for every aspect of medical care. Experts feel studies that pit one available treatment against another are the best answer. 

"What we really need are comparative effectiveness trials. That's what really informs guidelines. We're not doing enough," says study author Robert Califf of Duke University in Durham, N. C.

Drs. Terence M. Shaneyfelt and Robert M. Centor, of the Department of Medicine at the University of Alabama School of Medicine in Birmingham said, "Guidelines often have become marketing tools for device and pharmaceutical manufacturers. Only when likely biases of industry and specialty societies have been either removed or overcome by countervailing interests can impartial recommendations be achieved."

In argument that doctors who ignore the guidelines are less likely to provide top care is Dr. Douglas Weaver, president of the American College of Cardiology and head of cardiology at Henry Ford Hospital in Detroit, Michigan. He said, "I don't think we should be making freewheeling decisions in medical care," Weaver says. "Even guidelines that aren't based on definitive clinical trials are based on the best available information we have today."