Research questions usefulness of inflammation test to predict heart disease

<br>New research suggests that a blood test for inflammation isn't all that useful for predicting the risk of having a heart attack. <br><br>The study in Thursday's New England Journal of Medicine

Thursday, April 1st 2004, 12:00 am

By: News On 6

New research suggests that a blood test for inflammation isn't all that useful for predicting the risk of having a heart attack.

The study in Thursday's New England Journal of Medicine casts doubt on one of the hottest ideas in the field of heart disease _ that inflammation levels are a powerful indicator of heart disease.

And it challenges year-old recommendations from the U.S. government that doctors consider the test for some patients.

The researchers determined that inflammation is only a moderate predictor of heart disease. They concluded that the test doesn't contribute much to the predictive value of stronger risk factors such as high cholesterol, high blood pressure and smoking.

``There's no good scientific reason to be using it as a predictive test,'' said Dr. John Danesh, one of the British researchers at the University of Cambridge.

But a key U.S. researcher in the field had a different take on the findings, saying they confirm earlier studies and the use of the test. Dr. Paul Ridker of Harvard's Brigham and Women's Hospital in Boston contends inflammation is a strong risk factor and can spot people with no other signs of heart disease.

``My concern is that even in the face of overwhelming evidence that this inexpensive blood test works, we are at risk of moving backward rather than forward,'' said Ridker, who supports expanded use of the test.

Doctors can screen for low-level inflammation in the bloodstream by testing for C-reactive protein, or CRP, which fights infection. The painless inflammation can come from minor infections or irritations somewhere in the body.

Many experts believe chronic inflammation can weaken the walls of arteries, causing fatty buildups to rupture and trigger heart attacks.

In the latest research, Danesh and his colleagues used data from an Iceland study of heart disease that began in 1967. They compared 2,459 people who had a heart attack or died of heart disease over 20 years of follow-up with 3,969 participants who did not have a heart attack. Frozen blood samples were tested for CRP levels.

The researchers calculated that those with higher levels of CRP had a 45 percent increased risk of heart disease compared with those with the lowest levels. The researchers also analyzed 22 studies on the topic and found that patients with higher CRP levels had a 50 percent higher risk of heart disease.

That is far less than the early studies indicated. Eleven of the 22 studies analyzed were done before 2000, and together they showed a 100 percent increase in risk, or a doubling of the danger, the researchers said.

``It's a cautionary tale about how high the bar really needs to be before we roll out scientific advances into the community and into the clinic,'' Danesh said.

The researchers said their findings suggest that the recent recommendations for CRP testing should be reviewed. A co-author of the guidelines, however, defended them.

Dr. Thomas Pearson of the University of Rochester said the panel noted the weakness of the evidence and urged more study when it drew up the guidelines. He said the panel members were criticized by some as being too conservative.

``I think this is validating our conservatism,'' he said.

The guidelines, issued last year by the Centers for Disease Control and Prevention and the American Heart Association, do not support testing for everyone. They give doctors the option of testing those judged to be at 10 percent to 20 percent risk of heart disease, based on such factors as age, high cholesterol and high blood pressure.

Since then, many doctors have begun routinely screening patients for CRP.

Ridker said the Iceland study used a lower CRP level than his studies to determine risk in the highest group, which could account for the lower findings.

He is now studying whether using cholesterol-lowering statin drugs to bring down CRP levels in patients is beneficial. Diet and exercise can also lower CRP.