Friday, March 06, 2009

Official guidelines on how to treat heart problems largely based on weak evidence and expert opinion

The number of recommendations in the American Heart Association/American College of Cardiology (AHA/ACC) clinical-practice guidelines have progressively increased over time, but these recommendations are often based on weak evidence and expert opinion, a new study, published in the February 25, 2009 issue of the Journal of the American Medical Association, has shown.

Among guidelines reporting an update in recent years, the number of recommendations has increased 48% from the first to the current version, with the largest increase in recommendations for which there is conflicting evidence and/or a divergence of opinion about the efficacy of a procedure or treatment (class 2). In addition, roughly half of all recommendations are based on expert opinion, case studies, or standard of care rather than on data from multiple clinical trials or meta-analyses.

"It's a sobering result," lead investigator Dr Pierluigi Tricoci (Duke Clinical Research Institute, Durham, NC) told heartwire. "Almost half of the recommendations have a level of evidence C, meaning they have no supporting evidence or just a little supporting evidence. This means that situations where we are sure of what to do are small in number, while the situations where we are not so sure of what to do are the majority."

In this study, the investigators wanted to assess how the guidelines changed since the AHA/ACC began publishing clinical-practice guidelines more than 20 years ago. The guidelines currently use a grading system based on the level of evidence and class of recommendation. The level of evidence—A, B, or C—includes a description of the existence and types of studies available supporting the recommendation and expert consensus. The class of recommendation—1, 2, 2a, 2b, and 3—indicates the strength of the recommendation based on an objective judgment about the relative merits of the data.

From 1984 to 2008, the ACC/AHA issued 53 guidelines on 22 topics for a total of 7196 recommendations. Among these guidelines, 24 were disease-based, 15 were for interventional procedures, and 14 were for diagnostics. The disease-based and interventional-based guidelines were updated approximately every five years, while the diagnostic-procedure-based guidelines were updated eight years after the last publication.

Among guidelines with at least one revision, the number of recommendations increased 48% from the first guidelines to the most recent version. The increase in recommendations was driven primarily by increases in the number of class 2 recommendations—those with conflicting evidence and/or divergent opinions. Of the 16 current guidelines reporting levels of evidence, just 11% of recommendations were classified as evidence A, those based on data from multiple clinical trials or meta-analyses. Just under half of the recommendations, 48%, were based on expert opinion, case studies, or standards of care (level of evidence C).

Among the class 1 recommendations of guidelines reporting level of evidence, just 19% had a level of evidence A. There was also wide variation across the different specialties, with the disease-based and interventional-based guidelines having slightly better levels of evidence than the diagnostic-procedure guidelines. Roughly 70% of the recommendations within the valvular-heart-disease guidelines are evidence level C, with just one recommendation with evidence based on clinical trials. Heart-failure, secondary-prevention, and unstable-angina guidelines had the most recommendations based on clinical trial data or meta-analyses, or evidence level A. "Some fields are in better shape than others, but this is a general problem afflicting all the fields of cardiology," said Tricoci.

Ignore the guidelines altogether

In an editorial accompanying the published study [2], Drs Terrence Shaneyfelt and Robert Centor (University of Alabama School of Medicine, Birmingham) write that the "overreliance on expert opinion in guidelines is problematic," particularly since the guideline committees come to the table with implicit biases, values, and goals that aren't typically disclosed. Moreover, too many current guidelines are marketing- and opinion-based pieces, "delivering directive rather than assistive statements," they add.

In addition, they argue that guidelines are not patient-specific enough to be useful and do not allow for individualization of care, instead adopting a one-size-fits-all mentality. Moreover, there are simply too many guidelines on the same topic. The editorialists write that if the guidelines continue to exist, they need to undergo major changes, including limiting committee members with financial ties to industry or other potential conflicts of interest. Guideline development should also be centralized under a governing body to reduce bias and redundancy, something that might be achieved by allowing the US Department of Health and Human Services to oversee their drafting.

"However, it seems unlikely that substantial change will occur because many guideline developers seem set in their ways," write Shaneyfelt and Centor. "If all that can be produced are biased, minimally applicable consensus statements, perhaps guidelines should be avoided completely. Unless there is evidence of appropriate changes in the guideline process, clinicians and policy makers must reject calls for adherence to guidelines."

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Fewer calories=less weight, regardless of carb, fat, or protein content

And in any case the weight loss is small and soon reverses

It may be one of the most commonsense observations ever to be validated in a diet study: people lose weight if they eat fewer calories, regardless of where those calories come from. That's the upshot of a two-year study by Dr Frank Sacks (Harvard School of Public Health, Boston, MA) and colleagues, published in the February 26, 2009 issue of the New England Journal of Medicine.

After two years, 811 overweight adults randomized to one of four heart-healthy diets, each emphasizing different levels of fat, protein, and carbohydrates, showed similar degrees of weight loss. On average, patients lost 6 kg in six months, but gradually began to regain weight after 12 months, regardless of diet group.

According to Sacks, the research should help quell some of the debate—fostered by decades of research and fad diets—over what types of foods should be emphasized to produce weight loss. "Research has looked at whether carbohydrate is more satiating than fat, or whether protein is more satiating than carbohydrates, or whether overeating fat puts more fat in the belly than overeating carbohydrates, etc," Sacks explained. "So what's concerned colleagues of mine on the nutrition guideline panels in the past is the possibility that if we say that a 40% fat diet is okay, that maybe that would lead to weight gain. But where this study is going to be helpful is in saying 40% fat, 20% fat, it doesn't matter. If people can maintain a calorie deficit no matter what type of diet they were on, they're going to lose weight."

Sacks, who is incoming chair of the AHA's Nutrition Committee, acknowledged that nutrition advice in the past has worried too much about fat in the diet. "I'm very concerned that we maintain the focus on calories and keep the focus off percent calories from fat," he said.

An editorial accompanying Sacks et al's study applauds the duration of the study and the low dropout rate but takes a dimmer view of the weight loss achieved in the study and the ability of dieters to adhere to their diets over time. "Even these highly motivated, intelligent participants who were coached by expert professionals could not achieve the weight losses needed to reverse the obesity epidemic," Dr Martijn B Katan (VU University, Amsterdam, the Netherlands) writes. "The results would probably have been worse among poor, uneducated subjects. Evidently, individual treatment is powerless against an environment that offers so many high-calorie foods and labor-saving devices."

Sacks, speaking with heartwire, defended what he insisted was "clinically meaningful" weight loss in his study, emphasizing that many people achieved far greater losses than the average figure. Eckel, by contrast, was less sanguine, pointing out that an average weight loss of 3.5 kg at two years represents the best-case scenario, since real-life interventions rarely live up to the research setting.

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1 comment:

John A said...

Finaly a study of more than six months specifically targeting weight/diet.

And for about a year, participants lost weight and/or maintained the loss.

Then started to gain weight, starting to return to previous condition.

So is the conclusion that something other than a simplistic calorie count involved? Well, yes - availability of high-calorie foods and labor-saving devices. EVen though participants stayed on the diet, so how "availability" of stuff they were not eating pertains is not even given any thought - ie, if heroin is available you are at risk of being addicted, even if you never use it? And labor-saving devices: I suppose the participants bought items like washing machines where before being in the study they washed by hand?

The results were not quite as desired: instead of asking why, just throw out prejudiced statements about how you were destined to fail no matter what you did.