New guidelines issued Monday urge doctors to consider testing millions of Americans at moderate risk of heart disease for signs of inflammation in the bloodstream -- a newly recognized cause of heart attacks.
Evidence has been building for several years that painless inflammation is a major trigger of heart trouble, worse even than high cholesterol. But until now, doctors have been unsure how and when to look for the condition, which can be measured with a simple blood test.
The new recommendations, drawn up by the American Heart Association and the Centers for Disease Control and Prevention, are the first to propose an important role for inflammation testing as a way of judging whether people need aggressive treatment to protect their hearts.
The guidelines suggest limiting the testing to those already judged to be at 10 percent to 20 percent risk of heart disease over the next 10 years, based on such factors as age, high cholesterol and high blood pressure. This category is large, encompassing an estimated 40 percent of U.S. adults.
However, even in these patients, the test is considered optional and should be used only if it will help doctors decide whether they need treatment, which typically includes cholesterol-lowering drugs, better diets and losing weight.
The guidelines urge against testing people at very low risk, since those patients would probably not be put on treatment even if inflammation were found, as well as those already diagnosed with heart disease, since they should already be getting all standard treatments.
"The guidelines are very much oriented toward coming up with numbers that would alter your or your patients' behavior," said Dr. Thomas Pearson of the University of Rochester, co-chairman of the committee that wrote the statement.
The inflammation comes from many sources -- including possibly even gum disease and lingering urinary infections -- and triggers heart attacks by weakening the walls of blood vessels and making fatty buildups burst. It can be measured with a test that checks for C-reactive protein, or CRP, a chemical necessary for fighting injury and infection. The tests cost a few dollars to perform, and labs and hospitals charge between $10 and $120.
The cautiously worded statement is being published in Tuesday's issue of the journal Circulation. Pearson said it struck a balance between those who argue every adult should get a CRP test and those who reject any use, in part because they fear it will draw attention away from cholesterol lowering.
Dr. Eric Topol, cardiology chief at the Cleveland Clinic, called the guidelines "a dramatic advance" but wished they recommended testing for everyone at intermediate or high risk.
"In medicine, advances and changes in practice come slowly, unfortunately, so this set of recommendations is typical of a burgeoning field where the evidence overrides the ability of a group of experts to come to consensus," Topol said.
Much of the evidence backing the importance of inflammation in heart disease comes from the research of Dr. Paul Ridker of Boston's Brigham and Women's Hospital. One of his latest studies, conducted in women, found that half of all heart attacks and strokes occur in people with seemingly safe cholesterol levels, and that those with high CRP have double the risk of women with low levels.
"These recommendations are exceptionally conservative but very important," Ridker said. He said CRP is the first new blood test to be accepted for checking heart disease risk since cholesterol screening became standard about 30 years ago.
CRP can be lowered by the same strategies that bring down cholesterol -- exercising, losing weight, giving up smoking and taking statin drugs.
For now, Pearson said the field lacks gold standard studies showing that measuring and treating elevated CRP helps people live longer. However, such experiments are under way.
One, directed by Ridker and financed by AstraZeneca, will test the statin rosuvastatin, which is not yet approved for routine prescription in the United States. It will involve about 15,000 men and women with no history of heart trouble, cholesterol in the safe range and CRP above two milligrams per deciliter of blood.
The average CRP reading in the United States is 1.5. Ridker's studies show the risk is dramatically higher when levels hit 3.
EDITOR'S NOTE: Medical Editor Daniel Q. Haney is a special correspondent for The Associated Press.
On the Net: